Rothamsted Meteorological Station

  • Experiment Code: RMS
  • Experiment Site: Rothamsted
  • Description: Sir John Lawes, the founder of Rothamsted, realized that to understand crop growth, it was important to have records of the weather. Weather records also help us to understand the spread of crop diseases and insect behaviour. Rainfall and wind direction have been measured at Rothamsted every day since 1853, temperature since 1878 and sunshine since 1890, making this one of the longest sets of meteorological (weather) data available in the UK.
  • Date Start: 1843
  • Establisment Period End: 1951
  • Date End: Ongoing

Key Contacts

  • Andy Macdonald

  • Role: Principal Investigator
  • Organisation: Rothamsted Research
  • Address: West Common, Harpenden, Hertfordshire, AL5 2JQ, United Kingdom

  • Sarah Perryman

  • Role: Data Manager
  • Organisation: Rothamsted Research
  • Address: West Common, Harpenden, Hertfordshire, AL5 2JQ, United Kingdom

  • Margaret Glendining

  • Role: Data Manager
  • ORCID: https://orcid.org/0000-0002-6466-4629
  • Organisation: Rothamsted Research
  • Address: West Common, Harpenden, Hertfordshire, AL5 2JQ, United Kingdom

Funding

  • The e-RA database, including the published datasets generated from it, is part of the Rothamsted Long-Term Experiments - National Bioscience Research Infrastructure (RLTE-NBRI) , which also includes the Long-Term Experiments, the Sample Archive and Rothamsted's environmental monitoring activities including the weather stations and its role in the UK Environmental Change Network.
  • The RLTE-NBRI is supported by the Lawes Agricultural Trust and the Biotechnology and Biological Sciences Research Council (Grants BBS/E/C/00005189 (2012-2017); BBS/E/C/000J0300 (2017-2022); BB/CCG2280/1 (2023-2028)).

Experimental Design

Site: Rothamsted Met station - Rothamsted

  • Experiment Site: Rothamsted
  • Description: Description of the Met Station
  • Management: More desctiption of met station / related to managment
  • Visit Permitted?: Yes
  • Visiting Arrangments: Contact Andy Macdonald
  • Elevation: 130 Metres
  • Geolocation:    51.806876, -0.360137

Datasets available

Title (hover for a longer description) Year of Publication Type Identifier Version

Weather data - 30 year means

Rothamsted 30-year mean meteorological data 1961-1990 2019 Summary 10.23637/OARES30YrMeans6190
 01
Rothamsted 30-year mean meteorological data 1971-2000 2019 Summary 10.23637/OARES30YrMeans7100
 01
Rothamsted 30-year mean meteorological data 1981-2010 2019 Summary 10.23637/OARES30YrMeans8180
 01
Rothamsted 30-year mean meteorological data 1991-2020 2021 Summary 10.23637/OARES30YrMeans9120
 01

Weather data - Rainfall

Total Monthly Rainfall at Rothamsted March 1853 - July 2018 2018 Summary 10.23637/RMMRAIN5318
 01
Mean monthly rainfall at Rothamsted October 1985-September 2017 2020 Summary 10.23637/rmsMMRain10850917
 01

Weather data - Temperature

Annual Mean Air Temperature at Rothamsted 1878-2022 2023 Summary 10.23637/rms-RMAAtemp-03
 03
Annual Mean Air Temperature at Rothamsted 1878-2019 2020 Summary 10.23637/rms-RMAAtemp-02
 02
Annual Mean Air Temperature Anomaly at Rothamsted 1878-2019 2020 Summary 10.23637/rms-RMAAtempanomaly-1
 01
Mean monthly temperature at Rothamsted October 1985-September 2017 2020 Summary 10.23637/rmsmmtemp10850917
 01
Annual Mean Air Temperature at Rothamsted 1878-2013 2017 Summary 10.23637/KeyRefOARESmatemp
 01
.

Images

ARG100 rain gauge within turf wallARG100 rain gauge within turf wall eRA Curator
AnonometerAnonometer eRA Curator
Below drainage gauge (bare soil percolation)Below drainage gauge (bare soil percolation) eRA Curator
Campbell-Stokes Sunshine Recorder (discontinued)Campbell-Stokes Sunshine Recorder (discontinued) eRA Curator
Drainage gauges (bare soil percolation)Drainage gauges (bare soil percolation) eRA Curator
ECN atmospheric chemistry instrumentECN atmospheric chemistry instrument eRA Curator
Historical document rain gaugeHistorical document rain gauge eRA Curator
Historical document rain gauges with laddersHistorical document rain gauges with ladders eRA Curator
Inside Stevenson Temperature Screen (Max/Min Thermometers; Dry and Wet Bulb)Inside Stevenson Temperature Screen (Max/Min Thermometers; Dry and Wet Bulb) eRA Curator
Manual recording of Wind RunManual recording of Wind Run eRA Curator
Met Office tipping bucket rain gauge (now replaced)Met Office tipping bucket rain gauge (now replaced) eRA Curator
RES rain gauge - thumbnailRES rain gauge - thumbnail eRA Curator
RES sun recorder - thumbnailRES sun recorder - thumbnail eRA Curator
RES thermometers - thumbnailRES thermometers - thumbnail eRA Curator
RES wind tower - thumbnailRES wind tower - thumbnail eRA Curator
Soil thermometers under grass at 30, 50 & 100cm (dicontinued - replaced by electronic sensors)Soil thermometers under grass at 30, 50 & 100cm (dicontinued - replaced by electronic sensors) eRA Curator
Stevenson Temperature ScreenStevenson Temperature Screen eRA Curator
Stevenson Temperature Screen (closed)Stevenson Temperature Screen (closed) eRA Curator
Stevenson screenStevenson screen eRA Curator
Turf wall and wind towerTurf wall and wind tower eRA Curator
Wind instrumentsWind instruments eRA Curator
Wind recording instrumentsWind recording instruments eRA Curator
Wind tower - 10m mast with Wind Vane, Wind Speed Cup Anemometer and Radiation PyranometerWind tower - 10m mast with Wind Vane, Wind Speed Cup Anemometer and Radiation Pyranometer eRA Curator
Wind tower - 10m mast with Wind Vane, Wind Speed Cup Anemometer and Radiation PyranometerWind tower - 10m mast with Wind Vane, Wind Speed Cup Anemometer and Radiation Pyranometer eRA Curator
30 evaporation30 evaporation eRA Curator
30 max temp30 max temp eRA Curator
30 mean temp30 mean temp eRA Curator
30 min temp30 min temp eRA Curator
30 radiation30 radiation eRA Curator
30 rain30 rain eRA Curator
30 soil 100cm30 soil 100cm eRA Curator
30 soil 30cm30 soil 30cm eRA Curator
30 sunhours30 sunhours eRA Curator
30 wind30 wind eRA Curator
5raingaugeandturfwall5raingaugeandturfwall eRA Curator
AnemometerAnemometer eRA Curator
Campbell Stokes Sunshine Recorder (discontinued) and Met Office Radiation PyranometerCampbell Stokes Sunshine Recorder (discontinued) and Met Office Radiation Pyranometer eRA Curator
Centennial weather station presentation 2019Centennial weather station presentation 2019 eRA Curator
Grass minimum sensor (type 107)Grass minimum sensor (type 107) eRA Curator
Ladder down to rain gauge below 40inchLadder down to rain gauge below 40inch eRA Curator
Large Temperature Screen with Max/Min/Dry bulb & Wet Bulb thermometers with ThermographLarge Temperature Screen with Max/Min/Dry bulb & Wet Bulb thermometers with Thermograph eRA Curator
Looking into area below 40inchLooking into area below 40inch eRA Curator
MK11 cylindrical rain gauge within turf wall enclosureMK11 cylindrical rain gauge within turf wall enclosure eRA Curator
Met station turf wall foregroundMet station turf wall foreground eRA Curator
New thousand acre gauge 2011New thousand acre gauge 2011 eRA Curator
Rain gaugesRain gauges eRA Curator
Rothamsted Meteorological Station (Harpenden) (Met Office location Rothamsted No. 2)Rothamsted Meteorological Station (Harpenden) (Met Office location Rothamsted No. 2) eRA Curator
Rothamsted rain & drain gauges etching in The Gardeners Chronicle 1877Rothamsted rain & drain gauges etching in The Gardeners Chronicle 1877 eRA Curator
Soil temperature measurment under grass at 30, 50 & 100cm (discontinued - replaced by electronic sensors)Soil temperature measurment under grass at 30, 50 & 100cm (discontinued - replaced by electronic sensors) eRA Curator
Stevenson Temperature ScreenStevenson Temperature Screen eRA Curator
Temperature stripes 1878 2019 based on Rothamsted Mean Annual TemperatureTemperature stripes 1878 2019 based on Rothamsted Mean Annual Temperature eRA Curator
Thousandth of an acre rain gauge with stainless steel funnel (previously lead)Thousandth of an acre rain gauge with stainless steel funnel (previously lead) eRA Curator
Turf wall and rain gaugesTurf wall and rain gauges eRA Curator
Wind Vane, Wind Speed Cup Anemometer and Radiation Pyranometer at top of 10m mastWind Vane, Wind Speed Cup Anemometer and Radiation Pyranometer at top of 10m mast eRA Curator
Wind Vane, Wind Speed Cup Anemometer and Radiation Pyranometer at top of 10m mastWind Vane, Wind Speed Cup Anemometer and Radiation Pyranometer at top of 10m mast eRA Curator
ty_new thousand acre gaugety_new thousand acre gauge eRA Curator
x30 evaporationx30 evaporation eRA Curator
x30 max tempx30 max temp eRA Curator
x30 mean tempx30 mean temp eRA Curator
x30 min tempx30 min temp eRA Curator
x30 radiationx30 radiation eRA Curator
x30 rainx30 rain eRA Curator
x30 soil 100cmx30 soil 100cm eRA Curator
x30 soil 30cmx30 soil 30cm eRA Curator
x30 sunhoursx30 sunhours eRA Curator
x30 windx30 wind eRA Curator

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Weather 30-year means at Rothamsted

Updated 21-01-21 with new 1991-2020 mean data. Previous update 22-10-19

Rothamsted Research at Harpenden has the longest run of freely-available daily weather data in England and has been sending returns to the UK Meteorological Office since at least 1878. In 2017, Rothamsted was recognised by the World Meteorological Organization (WMO) as a Centennial Observation Station being one of the relatively small number of sites in the UK that has been recording reliable observations continuously for more than 100 years. Rainfall has been measured daily for more than 160 years, since 1853, using a 5-inch gauge and a much larger, and unusual, 1,000th of an acre gauge. Subsequently, other weather variables were added to the list including temperature from about 1878, sunshine hours from 1890, and wind force/speed from 1915. Weather variables were recorded manually until the end of 2003; an automatic data logger was installed to record the data electronically from 1st January 2004.

These daily weather data at Rothamsted has been summarised to generate 30-year mean sets of weather data :

In referring to these data sets, please use the approrporate DOI and citation available on those pages.

30-year mean maximum temperature

maximum temperature

30-year mean average temperature

mean temperature

30-year mean minimum temperature

minimum temperature

30-year monthly total rain fall

30-year rainfall

30-year mean total sunshine

30-year mean total sunshine

30-year mean daily radiation

30-year mean daily radiation

30-year mean wind speed

30-year mean wind speed

30-year mean soil temperature 30cm under grass

30-year mean soil temperature 30cm under grass

30-year mean soil temperature 100cm under grass

30-year mean soil temperature 100cm under grass

30-year mean evaporation

30-year mean evaporation

Note:

See the following citable webpages on this website for the data behind these charts;

Contact the e-RA Curators to arrange a password to download original raw daily weather data from the e-RA database.

Links:

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Curation Progress:

  • Empty draft made by Nath - 31/07/2020
  • Copied ld page - NCB - 31/07/2020
  • Note: the bit on Rothasmted is already on front page, then its about Brooms Barn and woburn: so I wonder if that is relevant...

Comment the div when good enough.

Background

Rothamsted has one of the longest continuous sets of meteorological recordings in the world. Total rainfall and wind direction have been measured since 1853, temperature since 1878, sunshine from 1890, wind force from 1917, radiation from 1931, wind run since 1946 and wind speed since 1960. Annual rainfall averages 704mm (1971-2000), but ranges widely from 380mm in 1921 to 973mm in 2000. Mean annual temperature 1878-1990 at Rothamsted was 9ºC; average annual temperature is now more than 1ºC higher than the 1878-1990 average (for more details refer to Guide to Classical Experiments 2006, p 44-45). Since January 1st 2004, meteorological records have been measured by a range of sensors attached to an automatic data logger; some manual observations continued to be made until May 2007.

Rothamsted took over the management of the farm at Woburn in the 1920's and the first meteorological records date back to 1928. Annual rainfall averages 649mm (1971-2000). Temperature, rainfall, sunshine, wind force and wind direction have been measured since 1928. Wind speed and wind run have been measured since 1968 and radiation measurements started in 1981. Manual observations ceased on 1st July 1999, and meteorological records are now measured by a range of sensors attached to an automatic data logger. The mean annual temperature (1971-2000) was 9.6 ºC.

Meteorological data was first collected in Brooms Barn in 1963. Fewer variables are measured than at Rothamsted and Woburn. Rainfall averages 612mm (1963-2008). Mean annual temperature 1964-2008 was 9.9°C. Dew point, wind run, sunshine hours, vapour pressure and relative humidity have also been measured and/or calculated. Data from 1982 is available in e-RA.

The Brooms Barn meteorological station is approx. 30m from the main buildings, which are approx. 10m high. This may cause some interference with the measurement of wind speed and wind direction, as ideally a mast with wind sensors should be a minimum of 10 times the height of the nearest building away from the nearest building (ie at least 100m apart). This gives enough fetch for the wind to settle down. The met station and main building have always been in these positions.

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Rothamsted Meteorological data available in ROTHMET

Daily meteorological data recorded at Rothamsted, Harpenden, Hertfordshire available from 1853. Since January 1st 2004, meteorological records have been measured by a range of sensors attached to an automatic data logger; some manual observations continued to be made until May 2007. The datalogger was updated from a CR23X to a CR3000 on 20/06/2019.

Hourly data from 2004 is available from the e-RA Curators.

Variable Units Description Dates recorded Methods of measurement

Air temperature
TMAX °C Maximum temperature 1878-current date

TMAX is recorded over the 24 hour period up to 0900GMT, for the previous day's maximum

TMIN is recorded over the 24 hour period up to 0900GMT, for the current day's minimum

Since 2004 recorded by thermistors (electronic temperature probes, Campbell Scientific, type 107). TMAX originally recorded using a mercury-in-glass sheathed column maximum thermometer and TMIN using a spirit-in-glass with indicator bar minimum thermometer, both housed in a naturally aspirating temperature screen.

TMIN °C Minimum temperature 1878-current date
WETB °C Wet bulb temperature, measuring temperature of evaporation 1915-January 2014

Recorded at 0900GMT

Since 2004 recorded by thermistor (electronic temperature probe, Campbell Scientific, type 107). Originally measured with a mercury-in-glass column thermometer, the bulb covered by a cotton wick kept moist from a water reservoir. Housed in a naturally aspirating temperature screen. Used to calculate relative humidity (RELH), vapour pressure (VAP) and dew point (DEWP).

Discontinued in January 2014 and replaced by a Relative Humidity Sensor to measure RELH.

DRYB °C Dry bulb temperature 1915-current date

Recorded at 0900GMT

Since 2004 recorded by thermistor (electronic temperature probe, Campbell Scientific, type 107). Originally measured with a sheathed mercury-in-glass column thermometer, housed in a naturally aspirating temperature screen. Used to calculate relative humidity (RELH), vapour pressure (VAP) and dew point (DEWP).

DEWP °C Dew point 1915-current date;

Recorded at 0900GMT

Derived from DRYB and RELH since 2014, after the method of Buck (1981). (see derived variables), calculated within the datalogger.

Derived from DRYB and WETB until 2013, (see derived variables), calculated within the datalogger. Before 2004 it was calculated from hygrometric tables.

GRSMIN °C Grass minimum temperature 1909-current date

Recorded at 0900GMT

Since 2004 recorded by thermistor (electronic temperature probe, Campbell Scientific, type 107), approx. 1cm above grass surface, measurement period 1800-0900GMT, measured according to Met Office Procedure. Previously recorded using a glass sheathed spirit-in-glass with indicator bar minimum thermometer, with bulb just touching grass surface, with cotton sleeve and anti-condensation shield on upper part of the instrument, minimum temperature 0900-0900GMT.

Soil temperature under grass
G10T °C Soil temperature under grass at 10cm 1931-current date

Recorded at 0900GMT

Since 2004 recorded by thermistors (electronic temperature probes, Campbell Scientific, type 107), buried in the soil at the appropriate depth.

First recorded using specially adapted thermometers set at depths of 4, 8, 12, 24 and 48 inches (10, 20, 30, 61 and 122cm) under grass cover. Since 1972, re-set to 10, 20, 30, 50 and 100cm (Penman 1974). G10T, G20T and G30T were in direct contact with the soil. G30T was discontinued in 1997.

The thermometers used to record E30T, E50T and E100T were encased in a glass sheath in a metal tube, enabling easy removal to read the temperature. The bulb was set in paraffin wax to minimize rapid temperature fluctuations when the thermometer was removed from the soil.

G20T °C Soil temperature under grass at 20cm 1931-current date
G30T °C Soil temperature under grass at 30cm 1931-1997
E30T °C Soil temperature under grass at 30cm 1915-1957; 1997-current date
E50T °C Soil temperature under grass at 50cm 1948-current date
E100T °C Soil temperature under grass at 100cm 1945-current date

Soil temperature under bare soil
S10T °C Bare soil temperature at 10cm 1931-current date

Recorded at 0900GMT

Since 2004 recorded by thermistors (electronic temperature probes, Campbell Scientific, type 107), buried in the soil at the appropriate depth.

First recorded using specially adapted thermometers set at depths of 10, 20 and 30cm (4, 8 and 12 inches) under bare soil (S10T, S20T and S30T). S10T and S20T were in direct contact with the soil. The thermometers used to measure S30T were encased in a glass sheath in a metal tube, enabling easy removal to read the temperature. The bulb was set in paraffin wax to minimize rapid temperature fluctuations when the thermometer was removed from the soil.

S20T °C Bare soil temperature at 20cm 1931-current date
S30T °C Bare soil temperature at 30cm 1931-current date

Rainfall (precipitation)
RAIN mm Rainfall from original 5 inch gauge 1853-1879; 1914-current date

Total rainfall over 24 hours recorded at 0900GMT

RAIN was originally recorded in a 5 inch (12.7cm) diameter rain gauge built in a garden near the laboratory in 1852. The water collected was measured in a graduated cylinder until about 1880. The gauge was then moved to the current meteorological enclosure. In 1948, a 12.7cm (5 inch) copper rain gauge of Meteorological Office standard was installed within a 0.3 m high, 1.5 m radius turf wall retained by brick to reduce wind eddies.

Since Sept 9th 2020 it has been recorded with an SBS500 tipping bucket rain gauge, funnel diameter 25.2cm and calibrated to tip at 0.2mm, manufactured by Environmental Measurements Ltd (EML), supplied and calibrated by Campbell Scientific. It is no longer sited within the turf wall, as the aerodynamics of the gauge means that it should not be affected by wind eddies. From 2004 to 8th Sept 2020 it was measured by an electronic tipping bucket rain gauge of 25.4cm (10 inch) diameter, ARG100 (manufactured by EML, supplied and calibrated by Campbell Scientific), calibrated to tip at 0.2mm, within the original turf wall. The old 5 inch manual copper rain gauge is still used to manually measure precipitation fallen as snow when the tipping bucket rain gauge is blocked with snow or ice.

Data from RAIN is missing between 1880-1914, and it is recommended that for a complete run of data from a standard rain gauge RAIN5 should be used for 1880-1914.

"Missing values" There are many instances before 2004 when no data is shown for RAIN (rather than zero). This is because a 'trace' of rain, snow, mist, dew or fog was manually recorded. A 'trace' is less than 0.05mm. For most purposes a missing value can be assumed to be zero.

EML state that the "ARG100 rain gauge typically captures over 5% more rainfall than most traditionally-shaped cylindrical gauges due to its unique aerodynamic shape and reduced evaporation-loss properties". This has found to be the case at Rothamsed. A review of the differences in rainfall capture between the ARG100 and the manual 5 inch gauge at Rothamsted was conducted. Using a double mass curve analysis, annual data from 1990-2017, and looking at each added year from 2004 (when the ARG100 was introduced), the overall correction factor is 1.1 or 10%. This means that the ARG100 captures 10% more rainfall than the manual 5 inch gauge. This correction is only applicable to annual and monthly totals, and to the variable RAIN at Rothamsted (ie ROTHMET only). It is not applicable to RAINL or RAIN5. To convert 5 inch data to ARG100 data, multiply by 1.1. To convert ARG100 data to 5 inch, divide by 1.1. We recommend that when you download data that spans both gauges, you multiply the 5 inch data by 1.1. Please contact the e-RA Curators for more information.

RAIN5 mm Rainfall from second 5 inch gauge 1873-1987

Total rainfall over 24 hours recorded at 0900GMT

The variable RAIN5 was originally recorded in another 5 inch (12.7cm) cooper rain gauge, established in 1873. Data was not recorded in e-RA after 1987. RAIN and RAIN5 are two separate gauges, hence the values do not exactly agree.

Data from RAIN is missing between 1880-1914, and it is recommended that for a complete run of data from a standard rain gauge RAIN5 should be used for 1880-1914.

"Missing values" There are many instances before 1987 when no data is shown for RAIN5 (rather than zero). This is because a 'trace' of rain, snow, mist, dew or fog was manually recorded. A 'trace' is less than 0.05mm. For most purposes a missing value can be assumed to be zero.

RAINL mm Rainfall in the 1/1000th acre rain gauge, to be used with the drainage data (DR20, DR40 and DR60) ONLY 1853-current date

Total rainfall over 24 hours recorded at 0900GMT

RAINL measures rain in a gauge of 1/1000th of an acre (4.047 sq metres), built in 1852/53. The gauge was constructed of timber with a lead funnel. Rain was collected daily in carboys and weighed to estimate the amount of rain. In 1873 a new gauge was installed and the carboys replaced by galvanized iron calibrated cylinders to measure rainfall. The old gauge was replaced by an identical new one in 1992. For the early history see Lawes et al., 1881.

From 2004 onwards the calibrated cylinders were replaced by an electronic tipping bucket rain gauge ARG100 (manufactured by Environmental Measurements Ltd (EML), supplied and calibrated by Campbell Scientific), calibrated to tip with every 0.0025mm of rain. In July 2010 the lead lining was stolen and it was replaced by a new stainless steel funnel of grade 316 and dimensions 2213mm x 1829mm in February 2011. No RAINL data was collected for this period.

Since 2004, when the met station was automated, RAINL may have been underestimating rainfall when rain is intense. RAINL should only be used in conjunction with the drainage data, which has the same surface area (DR20, DR40, DR60). For general daily rainfall data please use RAIN. It is recommended that if you use RAINL, RAIN should be used as a check.

"Missing values" There are many instances before 2004 when no data is shown for RAINL (rather than zero). This is because a 'trace' of rain, snow, mist, dew or fog was manually recorded. A 'trace' is less than 0.05mm. For most purposes a missing value can be assumed to be zero.

RDUR hr Rainfall duration 1931-current date

Total hours of rainfall over 24 hours recorded at 0900GMT

Since 2004 measured by an electronic tipping bucket rain gauge ARG100 (manufactured by Environmental Measurements Ltd, supplied and calibrated by Campbell Scientific), used to record RAIN. Originally measured by a Negretti and Zamra natural siphon rain recorder. Rain was collected in a float chamber and recorded on a daily chart on a clock drum, which recorded 10mm of rain before siphoning began and the recording restarted at the bottom of the chart. In 1978 this was replaced with a Cassella recorder with a diameter of 20.3cm.

Drainage data (percolation)
DR20 inches Drainage from drain gauge at 20 inch (51cm) depth 1870-current date

Total drainage over 24 hours recorded at 0900GMT

Three drain gauges (DR20, DR40 and DR60) were constructed at Rothamsted in 1870. They consist of undisturbed blocks of soil 20, 40 and 60 inches (51, 102 and 152 cm) deep and are equal in area to the rain gauge of 1/1000th of an acre (RAINL).

The gauges were constructed by digging under and around the block of soil, placing perforated plates underneath at the required depth and bricking up the sides. The soil around the gauges remained undisturbed throughout the construction process.

From 2004 to May 2023 drainage was measured by electronic tipping bucket rain gauge ARG100 (manufactured by Environmental Measurements Ltd (EML), supplied and calibrated by Campbell Scientific). Drain water was originally measured by weighing the carboys of collected water (as for RAINL), but these were replaced by calibrated cylinders. All three drain gauges remain as originally built. The soil has never been deep cultivated or cropped and the top is kept clear by hand weeding.

In May 2023 the ARG100 gauges were replaced by KALYX electronic tipping bucket rain gauges (supplied and callibrated by Campbell Scientific Ltd) funnel diamter 12.7cm (5"). The 20" gauge was replaced on 18/05/2023; the 40" and 60" gauges on 19/05/2023.

DR40 inches Drainage from drain gauge at 40 inch (102cm) depth 1870-current date
DR60 inches Drainage from drain gauge at 60 inch (152cm) depth 1870-current date

Sunshine
SUN hr Hours of sunshine 1890-current date

Total sun hours over 24 hours, 0000GMT to 2400GMT

Since May 2022 sunshine has been calculated using the Campbell-Stokes equation from solar radiation measured using a CMP3 Kipp and Zonen thermopile pyranometer. From 2004 until April 2022 it was calculated using a CM3 Kipp and Zonen thermopile pyranometer. Originally recorded using a Campbell-Stokes sunshine recorder. The sun's rays are focused onto a card (treated to prevent it from catching fire) and the brown scorch mark on the card is then measured. The cards are of varying lengths applicable to the time of year (winter, equinox, and summer).

Radiation
RAD J/cm2 Total solar radiation 1931-current date

Total over 24 hours, 0000GMT to 2400GMT

Total solar radiation measured since May 2022 by a CMP3 Kipp and Zonen thermopile pyranometer. From 2004 until April 2022 measured by a CM3 Kipp and Zonen thermopile pyranometer. Recorded since 1921, but the data in e-RA are from 1931, as the early data was considered unreliable. Originally recorded with a Callendar radiation chart recorder. In 1955 this was replaced with a Moll-type solarimeter (Kipp) with a paper chart recording potentiometer. Daily totals were obtained by planimeter integration until 1958 when an automatic integrator was added. A Kipp integrator and recorder was used from 13th November 1975, and a Kipp and Zonen integrator installed in 1989.

All data before 1955 should be treated with caution. There was much uncertainty about the sensitivity of the equipment (Penman 1974). Radiation readings between 1947 and 1954 are around 20% higher than would be expected from sunshine hours, and much data is missing between 1947 and 1949.

Data are recorded as J/cm2. To convert to MJ/m2 divide by 100 (see Conversion factors).

Cloud
CLOUD okta Cloud cover 1915-2007

Recorded at 0900GMT

Observed cloud cover on a scale of 0 to 9 Oktas. 0 = the complete absence of cloud. 1 = a cloud amount of 1 eighth or less of the sky, but not zero, etc. 7 = a cloud amount of 7 eighths or more, but not full cloud cover. 8 = full cloud cover with no breaks. 9 = sky obscured by fog or other meteorological phenomena.

Wind
WDIR degrees Wind direction (0-360 degrees) (at 10m) 1853-current date

Recorded at 0900GMT

Wind direction (WDIR) has been recorded since 1853 and is measured by a wind vane. It is shown as an angle, going clockwise from North. 360 = North, 90 = East, 180 = South, 270 = West. The reading 0 (or 000) indicates that there is no wind, ie the windspeed is 0 m/s. A WDIR reading of 0 with a windspeed greater than 0 implies that the WDIR is 360 degrees (North).

Since 21/04/2022 WDIR has been measured by an electronic wind vane (Vector Instruments, W200P) installed at 10m above ground level. Between 2004 and April 2022 it was recorded by a W200P wind vane at a height of 12.8m above ground level. The standard height for surface wind measurements over open and level terrain is 10m. However, no correction is needed for wind measured between 8 and 13m (Met Office, 1982). We therefore assumed a mid-point height of 10m. From 2004 WDIR has been calculated as an average over 10 minutes from 0850 to 0900GMT.

From 1978 (WDIR) was measured by a wind vane linked to a Munro roll chart recorder (model IM175). Previously it was estimated from a wind vane with fixed ordinal points.

WFORCE code Wind force in Beaufort scale (0-12) 1915-1959

Recorded at 0900GMT

Wind speed was first estimated using the Beaufort scale, which describes wind force on a scale of 0 (no wind) to 12 (hurricane) based on observations of the movement of smoke, leaves, branches, etc. From 1960 onwards this was replaced by direct measurements of wind speed (WINDSP).

The Beaufort scale can be converted to wind speed: V = 0.836 x SQRT (B3)

where V is the equivalent wind speed (m/s) at 10 metres above ground level and B is Beaufort scale number (see Conversion factors).

WINDSP m/s Wind speed (at 10m) 1960-current date

Recorded at 0900GMT

Direct measurement of wind speed (WINDSP) by cup anemometer replaced the visual assessment of windspeed (WFORCE) based on the Beaufort scale in 1960.

Since 21/04/2022 WINDSP has been recorded by electronic cup anemometer (Vector Instruments, A100LK/2) installed at a height of 10m above ground level. From 2004 until April 2022 it was recorded by electronic cup anemometer (Vector Instruments, A100LK/2) installed at a height of 12.8m above ground level. The standard height for surface wind measurements over open and level terrain is 10m. However, no correction is needed for wind speeds measured between 8 and 13m (Met Office, 1982). We therefore assumed a mid-point height of 10m.

From November 1977 it was measured by a cup anemometer linked to a Munro roll chart recorder (model IM175). Previously it was measured with a Dines anemometer.

WINDSP and WFORCE are point values, recorded at 0900GMT. From 2004 WINDSP has been calculated as an average over 60 seconds sampled at 0900GMT.

Average daily (24 hour) windspeed can be calculated from total daily WINDRUN, correcting for height (see Conversion factors).

WINDRUN km Run of Wind (at 2m) 1946-current date

Total run of wind in 24 hours, recorded at 0900GMT

WINDRUN measures the total 'run' (distance) of wind in 24 hours. It is measured by a cup anemometer. Since February 1st 2014 it has been recorded by an electronic cup anemometer (Vector Instruments A100LK) at the standard height of 2m above ground level.

Recorded from February 4th 2004 to January 2014 with an electronic cup anemometer (Vector Instruments, A100LK/2) at 12.8m above ground level, downscaled to the 2m equivalent by multiplying by 0.78 (see Conversion factors)

From 1946 to February 3rd 2004 recorded manually using a cup anemometer with a calibrated meter at the standard height of 2m.

Diary

Daily observations, based on standard Met Office weather codes. Discontinued 1978 or mid 2007.
DYHAIL Code Code indicating type of hail 1960-1988; 1998-2007

Recorded at 0900GMT

Manual observations indicating if hail was present during the day, and if so, what type. Code 0-7. 1 = Ice prisms; 2 = Snow grains; 3 = Snow pellets; 4 = Ice pellets; 5 = Hail (5-9mm diameter); 6 = Hail (10-19mm diameter); 7 = Hail (20mm diameter or more). Null or code 0 = No Hail.
DYSNOW Code Code indicating day with snow or sleet 1960-88; 1998-2007

Recorded at 0900GMT

Manual observations recording if snow or sleet was present. Code 1 = sleet, code 5 = snow crystals. Code 0 = no snow.
DYTHUN Code Code indicating day with thunder 1960-1988; 1998-2007

Recorded at 0900GMT

Manual observations recording if thunder was present. Code 1 = thunder during the day, code 0 = no thunder during the day.
FOG Code Code indicating day with fog 1960-1978

Recorded at 0900GMT

Manual observations recording if fog was present. Code 1 = fog present, code 0 = no fog.
SNOWL Code Code indicating whether snow lying 1960-1978

Recorded at 0900GMT

Manual observations recording if snow was present. This may have been snow from a previous day. See FSNOWD for depth of freshly fallen snow for the current day. Code 1 = snow present, code 0 = no snow.

SNOWD mm Total depth of snow 1960-2007

Recorded at 0900GMT

Manual recording of total depth of lying snow at the time of observation. This may have been snow from a previous days. See FSNOWD for depth of freshly fallen snow for the current day.

FSNOWD mm Depth of freshly-fallen snow 1960-1978

Recorded at 0900GMT

Manual recording of total depth of freshly-fallen snow.

Other selected fields
RELH % Relative humidity 1925-current date

Recorded at 0900GMT

Since August 7th 2018 measured by a Relative Humidity sensor EE181 (manufactured by E+E Elektronic Corporation, supplied and calibrated by Campbell Scientific). This replaced the MP100A RH Sensor (manufactured by Rotronics, supplied by Campbell Scientific) installed in late 2013. Previously derived from WETB and DRYB (see derived variables).

BAR mb Barometric pressure 1915-1959; 1977-2003

Recorded at 0900GMT

Atmospheric pressure was measured with a mercury barometer until 2003. For further details, see Met Office (1982) p 103.
THERM °C Attached thermometer reading for barometric pressure 1915-1959

Recorded at 0900GMT

A thermometer attached to the instrument casing, known as the attached thermometer, was used to measure the temperature of the mercury column from which the density of the mercury was established. The barometer and attached thermometer were kept indoors. For further details, see Met Office (1982) p 103.
BAR_MSL mb Air pressure at Mean Sea Level (MSL) 1950-1977

Recorded at 0900GMT

Atmospheric pressure corrected to Mean Sea Level was measured with a mercury barometer. For further details, see Met Office (1982) p 103.
VAP mb Vapour pressure 1946-current date

Recorded at 0900GMT

Since January 15th 2014 derived from RELH and DRYB after the method of Buck (1981), calculated within the datalogger. Previously derived from DRYB and WETB (see derived variables).

VIS Code Visibility 1923-2007

Recorded at 0900GMT

Manual recording of visibility. Codes 0-9, E, X (1960-2007): CODE X = Dense fog. Visibility range 0-19m; CODE E = Dense fog. Visibility range 20-39m; CODE 0 = Thick fog. Visibility range 40-99m; CODE 1 = Thick fog. Visibility range 100-199m; CODE 2 = Thick fog. Visibility range 200-399m, CODE 3 = Moderate fog. Visibility range 400-999m; CODE 4 = Very poor visibility, range 1000-1999m; CODE 5 = Poor visibility, range 2000-3999m; CODE 6 = Moderate visibility, range 4-9km; CODE 7 = Good visibility, range 10-19km; CODE 8 = Very good visibility, range 20-39km; CODE 9 = Excellent visibility, range 40km or over.

Codes A-M, (1923-1959, 1960-2007 equivalent code in brackets): CODE A (E) = Dense fog. Visibility range 18-22m; CODE B (0) = Thick fog. Visibility range 36-44m; CODE C (1) = Thick fog. Visibility range 90-110m; CODE D (2) = Fog. Visibility range 180-220m; CODE E (3) = Moderate fog. Visibility range 360-440m; CODE F (4) = Very poor visibility. Visibility range 900-1100m; CODE G (5) = Poor visibility. Visibility range 1.8-2.2 km; CODE H (6) = Moderate visibility. Visibility range 3.6-4.4km; CODE I (6) = Moderate visibility. Visibility range 6.3-7.7 km; CODE J (7) = Good visibility. Visibility range 9-11 km; CODE K (8) = Very good visibility. Visibility range 18-22km; CODE L (8) = Very good visibility. Visibility range 27-33km CODE M (9) = Excellent visibility. Visibility range 36-44km.

Key References

1982

  • Meteorological_Office(1982) "Observer's Handbook, 4th Edition, Met.0.933"

1977

1974

1948

  • Penman, H. L.(1948) "Natural Evaporation from open water, bare soil and grass", Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences, 193, 120-145
    DOI: 10.1098/rspa.1948.0037

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Extreme weather at Rothamsted

Last updated 5th July 2023.

Rothamsted Research at Harpenden has the longest run of freely-available daily weather data in England and has been sending returns to the UK Meteorological Office since at least 1878. In 2017, Rothamsted was recognised by the World Meteorological Organization (WMO) as a Centennial Observation Station being one of the relatively small number of sites in the UK that has been recording reliable observations continuously for more than 100 years. Rainfall has been measured daily for more than 160 years, since 1853, using a 5-inch gauge and a much larger, and unusual, 1,000th of an acre gauge. Subsequently, other weather variables were added to the list including temperature from about 1878, sunshine hours from 1890, and wind force/speed from 1915. Weather variables were recorded manually until the end of 2003; an automatic data logger was installed to record the data electronically from 1st January 2004*.

The Rothamsted weather records reflect many of the memorable national weather events such as the heatwaves of 1976, 2018 and 2022, the severe winters of 1947 and 1963, the heavy rainfall of December 2015, and the drought of 1921. The highs and lows include:

Extreme Days Back to top

Hottest day

The highest temperature at Rothamsted (Harpenden), since records began in January 1878, recently became 38.4 C on Tuesday 19th July 2022 (this beats the previous record at Harpenden of 36.7 °C on July 25th 2019). July 19th 2022 was also the record hottest day at the Rothamsted weather stations at Woburn in Bedfordshire, with 39.5 °C, and at Brooms Barn in Suffolk, with 38.8 °C.

The highest daily maximum air temperature recorded for every day of the year since records began in 1878 are available as a downloadable Excel file, click here : Daily Maximum Temperatures recorded at Rothamsted for each day of the year since records began in 1878 Seven of these are in 2022 so far; the highest number for one year was 15 record days in 2015; in 1957 there were 12 hottest days; in 1893 and 1906 there were 9 hottest days.

The 2022 European heat wave led to the hottest summer on record in Europe since at least 1540. Several weather records were broken in the United Kingdom, including the UK's highest recorded temperature of 40.3 C at Coningsby in Lincolnshire - the first time 40C has been exceeded in the UK since records began (surpassing the previous record of 38.7 °C in Cambridge on 25th July 2019).

Coldest day

The lowest temperature, since records began in January 1878, was -17.0 °C on 13th December 1981.

The winter of 1981-82 in the United Kingdom was called "The Big Snow of 1982" by the press (Wikipedia).

Original record sheet relating to the coldest day

Wettest day

The wettest day, since records began in February 1853, with 3.238 inches (82.2mm) rain was 26th June 1888.

The Times reported on July 12 1888: “Extraordinary weather for the time of year is reported from various parts of the country" with snow in the summer!

Original record sheets relating to the wettest day

The ten warmest days since records began in January 1878.

The ten warmest days (maximum temperatures) span more than 100 years at Rothamsted, from 1911, but seven of them were post-2000.

Rank Date Temperature °C
1 19th July 2022 38.4
2 25th July 2019 36.7
3 18th July 2022 35.7
4 10th August 2003 35.6
5 6th August 2003 34.2
6 3rd August 1990 33.8
7 9th August 2003 33.8
8 9th August 1911 33.5
9 1st July 2015 33.4
10 19th August 1932 33.3

The ten coldest days since records began in January 1878.

The ten coldest days (minimum temperatures) at Rothamsted were all pre-1982, with more than half of them pre-1900.

Rank Date Temperature °C
1 13th December 1981 -17.0
2 23rd January 1963 -16.7
3 7th February 1895 -16.4
4 8th February 1895 -15.8
= 5 17th January 1926 -15.6
= 5 24th January 1963 -15.6
7 24th February 1947 -15.3
8 21st January 1881 -15.0
9 7th December 1879 -14.9
= 10 8th January 1886 -14.4
= 10 10th February 1895 -14.4

Extreme months Back to top

The hottest and coldest months since records began in January 1878.

There are various ways to look at this data, this table shows just a few options.
Six of the warmest months were since 2000, whilst none of the coldest months were after 2000.

The highest monthly temperature ever recorded was July 2022 and the coldest month ever recorded was December 1981.
Two of the hottest months (January & February) and four of the coldest months (February, May, October & November) were in the 19th Century.

Highest mean maxiumum monthly temperature
Year
Lowest mean minimum monthly temperature
Year
Highest mean average monthly temperature
Year
Lowest mean average monthly temperature
Year
January
15.2
1888
-16.7
1963
6.8
1921
-3.4
1963
February
18.2
1891
-16.4
1895
7.0
1990
-2.7
1947
March
22.5
2021
-12.2
1965
8.9
1957
2.0
1883
April
26.7
2018
-6.2
1990
12.2
2011
4.7
1917
May
29.8
1947
-3.7
1886
13.5
1964
8.5
1879
June
33.0
1976
0.0
1962
17.3
2023
11.0
1916
July
38.4
2022
2.8
1965
20.3
2006
13.4
1919
August
35.6
2003
2.8
1921
19.6
2022
13.2
1912
September
32.7
1906
-1.1
1919
17.4
2006
11.0
1952
October
26.7
2011
-5.6
1887
13.4
2001
6.7
1919
November
19.1
1938
-8.3
1887
9.7
1994
2.5
1923
December
15.3
2015
-17.0
1981
9.9
2015
-1.9
1890

Bold indicates a record in the last year.

The wettest and driest months since records began in January 1853.

Half of the wettest months were since 2000. The driest months were all before 1990, with the exception of April 2021, five of the driest were in the 19th Century.

Highest Total Rainfall Year Lowest Total Rainfall Year
January 176.2 2014 8.1 1855
February 141.9 2014 0.9 1891
March 129.2 1979 1.2 1929
April 168.6 2012 1.6 2021
May 135.8 2007 1.5 1990
June 166.5 2012 2.5 1925
July 167.2 1855 4.1 1921
August 172.0 2020 1.7 1947
September 194.5 1896 0.9 1865
October 198.7 1987 1.1 1947
November 192.4 1940 4.0 1867
December 190.9 1914 4.7 1853

The sunniest and dullest months since records began in January 1890.

Five of the sunniest months were between 1975 and 1997, whilst seven of the dullest months were between and 1956 and 1996.

Highest Total Sunshine Year Lowest Total Sunshine Year
January 90.9 1984 22.2 1996
February 145.5 2008 22.5 1940
March 205.7 1907 45.2 1984
April 270.1 1893 84.7 1966
May 308.6 2020 116.9 1981
June 289.1 1975 115.2 1909
July 314.9 1911 90.8 1965
August 279.7 1995 75.8 1894
September 228.7 1895 32.6 1894
October 163.9 1997 46.3 1976
November 114.1 1989 26.5 1962
December 94.7 2014 12.3 1956

See Rothamsted Highs and Lows for complete records of variables and extreme months.

 

Extreme Years Back to top

Temperature extremes, since records began in January 1878.

The ten warmest years

At Rothamsted, the ten warmest "mean annual average" years have all occurred since 1999.

The warmest 'average annual temperature' years were 2014 and 2022 with mean annual temperatures of 11.2 °C.

Rank Year Mean annual average temperature degrees C
=1 2022 11.23
=1 2014 11.23
2 2020 11.09
3 2006 10.88
4 2011 10.84
5 2018 10.79
6 2002 10.63
7 2017 10.62
8 2003 10.55
9 1999 10.52
10 2007 10.49

At Rothamsted, most of the warmest "mean annual maximum" temperature years have occurred since 2000, but two were before 1950 (1921 and 1950):

Rank Year Mean annual maximum temperature degrees C
1
2022
15.52
2
2020
15.14
3
2014
15.10
4
2018
14.89
4
2003
14.89
5
2011
14.74
5
1949
14.74
6
1921
14.70
7
1989
14.67
8
2019
14.63
9
2006
14.62
10
1990
14.61

 

The ten coldest years

At Rothamsted, the ten coldest 'average annual temperature' years have all occurred before 1964, half of them were in the 19th Century. The coldest year was 1879 with a mean annual temperature of 7.3 °C.

Rank Year Mean annual average temperature degrees C
1 1879 7.27
2 1888 7.56
3 1963 7.94
4 1892 8.04
5 1887 8.11
6 1919 8.12
7 1917 8.14
8 1962 8.19
9 1922 8.36
10 1885 8.45

At Rothamsted, the ten coldest 'minimum annual temperature' years have also all occurred before 1964, seven of them were in the 19th Century. The coldest year was 1887 with a mean annual temperature of 3.7 °C.

Rank Year Mean annual minimum temperature degrees C
1 1887 3.73
2 1879 3.75
3 1892 3.79
4 1888 3.86
5 1963 4.08
6 1962 4.21
7 1919 4.22
8 1895 4.25
9 1891 4.31
10 1890 4.37

 

Rainfall extremes, since records began in February 1853.

The wettest year was 2012 with 1059.2mm total rainfall, the second wettest year was 2020 with 1032.8mm total rainfall.

The driest year was 1921 with 380.1mm total rainfall.

 

Sunshine extremes, since records began in 1893.

Sunniest Years

Seven of the sunniest years were since 1988, four of them since 2000. The sunniest year was 2022 with 1912.50 total sun hours:

Rank Year Total hours of sunshine in year
1 2022 1912.5
2 1989 1872.3
3 2003 1871.0
4 2018 1864.7
5 1929 1853.8
6 1995 1853.5
7 1893 1840.4
8 1990 1839.9
9 1906 1825.0
10 2020 1800.9

Cloudiest Years

The top ten cloudiest years were all prior to 1981, half of them were in the 1950s/60's. The cloudiest year was 1968 with 1149.2 total sun hours:

Rank Year Total hours of sunshine in year
1 1968 1149.2
2 1966 1274.7
3 1894 1277.4
4 1937 1278.1
5 1981 1286.3
6 1963 1288.4
7 1936 1292.8
8 1954 1303.0
9 1965 1317.3
10 1958 1324.0

 

See Rothamsted Highs and Lows for complete records of variables and extreme months.

Extreme Decades Back to top

Temperature extremes, averaged over decades, since records began in January 1878.

The last decade 2010-2019 had the warmest maximum daily average temperature ever recorded at Rothamsted since records began fourteen decades ago.

The decade with the warmest maximum daily average temperature (23.74°C) was 2010-2019

The decade with the coolest maximum daily average temperature (20.66°C) was 1960-1969

The decade with the warmest mean annual average temperature (10.38°CC) was 2000-2009

The decade with the coolest mean annual average temperature (8.67°C) was 1880-1889

The decade with the warmest minimum daily average temperature (-2.24°C) was 2000-2009

The decade with the coolest minimum daily average temperature (-5.79°C) was 1890-1899

Decade Maximum Daily Average Temperature Mean Annual Average Temperature Minimum Daily Average Temperature
1880-1889 20.92 8.67 -5.18
1890-1899 20.78 9.06 -5.79
1900-1909 21.24 9.00 -4.08
1910-1919 21.31 9.20 -3.17
1920-1929 21.41 9.04 -4.56
1930-1939 22.01 9.27 -3.45
1940-1949 22.72 9.38 -5.27
1950-1959 21.59 9.24 -4.26
1960-1969 20.66 8.97 -5.20
1970-1979 21.18 9.27 -3.59
1980-1989 21.42 9.24 -4.52
1990-1999 22.06 9.95 -2.99
2000-2009 22.88 10.38 -2.24
2010-2019 23.74 10.31 -2.70

Note: Even earlier records, in the form of a weather diary (as opposed to actual measurements), were made by Sir John Wittewronge, an ancestor of Sir John Lawes who also lived at Rothamsted Manor. These weather records provide a fascinating insight into weather conditions over five years at the end of the 17th Century (1684-1689) and give an indication of the weather experienced in Hertfordshire at a time when the Little Ice Age was affecting Europe ("'Observations of Weather' The Weather Diary of Sir John Wittewronge of Rothamsted 1684-1689". Edited by Margaret Harcourt Williams and John Stevenson and published in 1999 by Hertfordshire Record Society Publications).

*Some variables such as snow and cloud cover continued to be measured manually until May 2007. These trained observers who kept records before automation included Chris Hall, Arthur Day, John Croft, Dave Yeoman, Bob Norrish, Gavin Harrison, Helen Stevenson, Paul Hargreaves, Tim Hall, Edwin Grey and the first recorder, Thomas Wilson. The current weather recorder is Tony Scott.

If you would like to access the RAW records from the database, please fill in a request form.

News & Links:

Annual Mean Air Temperature at Rothamsted (1878-2013) e-RA Open Access data

World Meteorological Centennial Observing Stations WMO 2017

Centennial Recognition for 'Memories of Weather' Met Office December 2018

Major Contribution to Climate Science Recognised Rothamsted Research News December 2018

Rothamsted Research to be commemorated by the World Meteorological Organisation ITV News March 2019

WMO confrims past 4 years were warmest on record WMO February 2019

Met Office Weather Observations Website WOW

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History of the measurement of meteorological data at Rothamsted

Meteorological data has been measured at Rothamsted's Harpenden site since 1853. The earliest records are of rainfall and wind direction. Rainfall was originally recorded in a 5 inch (12.7cm) rain gauge in the garden of Rivers Lodge, a house next door to the Rothamsted Russell Building. The water collected was carried across to the laboratory and measured in a graduated cylinder. The gauge was moved to the meteorological enclosure in Barnfield in around 1880.

Thomas Wilson of Rivers Lodge was recording weather from at least 1873. In August 1876, he offered to 'keep a Meteorological register' for the Met. Office. There is, as far as we know, a continuous record from then until 1899. He undoubtedly submitted the vast majority of these returns but as he often failed to sign them it is possible that someone else (most likely Edwin Grey) was responsible for some of the later ones; the last one that Wilson signed was, we think, that for January 1897. The Rothamsted Archive has Wilson's original records (MET3.1) because he asked the Met. Office to return them after copying the figures. He inconsistently gave the location as Harpenden, Harpenden Common or Rivers Lodge but never (or, perhaps, very seldom) wrote Rothamsted.

Wilson made various observations (at Rivers Lodge) including temperature but his rainfall figures are from Rothamsted (i.e. the Barnfield site). This is not always specified but there are more than enough references to the fact to leave no doubt that this was invariably true.

Data from the Rothamsted rain and drain gauges are in MET2.2. From January 1878, the tables also record minimum and maximum temperatures, which are from Rivers Lodge. Again this is not always specified but it is indicated sufficiently frequently to be sure that it was invariably so. We checked figures for November 1884 in the two documents ( i.e. Wilson's return to the Met. Office and the Rothamsted rain and drain gauge tables) and confirmed that, for both rainfall and temperature, they are identical. It is likely that the temperature data in e-RA were copied from MET2.2 because both start on 1st January 1878; if the source was Wilson's original returns, the transcriber(s) would have been aware that the records started in August 1876.

There is potential to extend back by seventeen months the daily maximum and minimum temperatures in e-RA but it would be wise to first examine in more detail the correspondence in MET4.2, which is thought to make reference to the acquisition of a screen; it's possible that Wilson did not, at first, have a screen. As Wilson's figures also include wet and dry bulb temperatures there is even greater scope to add to the humidity data in e-RA, which currently start in 1915.

What happened after 1899 has not been established but nothing has been found to suggest that Wilson continued making returns to the Met. Office after that date. It is, however, almost certain that it was still Rivers Lodge data that were being submitted to them because Edwin Grey stated (in his 'Reminiscences'): 'The present collection of meteorological instruments now in use were obtained and set up in their present position by Sir Daniel Hall. Before these were acquired we used the records of Mr. Wilson's private instruments, the thermometer screen being in the grounds of River's (sic) Lodge and the barometer in the hall'. Hall came in 1902 and left in 1912 so, assuming that 'the present collection of meteorological instruments' to which Grey refers was on the Barnfield Met. Site, they can't have been in use before 1902. MET5.5 contains Edwin Grey's notebooks of 'Daily Meteorological Records' 1891-4 and, perhaps more significantly, 1897-1910; figures for the years up to 1902 can be assumed to be for Rivers Lodge even if that is not explicitly stated. We have found nothing to indicate when the Barnfield instruments were installed but, interestingly, there are in MET5.6, 'River's (sic) Lodge meteorological records, 1910-27'. Thus the Rivers Lodge instruments were being read until at least 1927, thus implying that observations were for some years being made on both sites (i.e. Rivers Lodge and Barnfield). It is, therefore, possible that, for some time after the new instruments had been installed on the Barnfield site, it was still Rivers Lodge data that were being sent to the Met. Office.

With thanks to John Jenkyn and Liz Allsopp who provided this background information, Jan 2018

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Rothamsted Met Data Monthly & Annual Summaries

August 2023: August was mainly dry with below average sunshine and air temperature.

Rainfall was below average with 50.5 mm (-21.49 mm). We had 16 days with 0.2 mm or more of rain, of which 3 days had more than 5.0 mm; the most was 9.7 mm on the 2nd.

The mean maximum and minimum air temperatures were below average with 21.2 ºC (-0.45 °C) and 12.2 ºC (-0.07 °C) respectively. The highest temperature was 25.3 ºC on the 10th. The lowest temperature was 9.1 ºC on the 31st.

Sunshine was below average with 182.9 hours (-6.51 hours). There were 0 days without sun and the sunniest day was the 10th with 11.9 hours.

There were no air frosts and no ground frosts.

Note: The average refers to the 30 year means 1991-2020.

July 2023: July was was cool, wet and particularly overcast.

Rainfall was 97.8 mm, which is 42.31 mm above average. We had 21 days with 0.2 mm or more of rain and 5 days with more than 5 mm. The greatest rainfall was 19.0 mm recorded on the 14th.

The average maximum and minimum air temperatures were below average at 20.9 °C (-1.10 °C) and 12.2 °C (-0.11 °C) respectively. The hottest day was the 7th reaching 28.2 ºC. The lowest minimum air temperature was 8.3 ºC on the 6th.

Sunshine was below average with 181.3 hrs (-25.49 hours). The most was 14.1 hours on the 7th and there was only 1 day when the sun didn’t shine.

There were no air frosts and no ground frosts.

Note: The average refers to the 30 year means 1991-2020.

June 2023: June was warmer, drier and sunnier than average.

Rainfall was 16.0 mm, which is 38.86 mm below average. We had 7 days with 0.2 mm or more of rain, of which 1 day had more than 5.0 mm. The most rainfall in a single day was 8.7 mm collected on the 28th).

The mean maximum air temperature and mean minimum air temperature were above average at 23.3ºC (+3.78 °C) and 11.2 ºC (+1.02 °C) respectively. The hottest day reached 29.8 ºC on the 25th. The coolest night was 6.6ºC on the 3rd. The mean daily air temperature of 17.3°C for June was the warmest on record.

Sunshine was 250.1 hours, which is 44.32 hours above average. There were 0 days without sun.

There were 0 air frosts and 0 ground frosts.

Note: The average refers to the 30 year means 1991-2020.

May 2023: May was warmer and drier than average with above average sunshine.

Rainfall was 48.9 mm, which is 4.38 mm below average. We had 11 days with 0.2 mm or more of rain, of which 4 days had more than 5.0 mm. The greatest fall of rain was 14.5 mm on the 8th).

The mean maximum and minimum temperatures were above average at 16.6 ºC (+0.07 °C) and 7.7 ºC (+0.40 °C) respectively. The highest temperature was 20.7 ºC on the 28th and the lowest temperature was 2.9 ºC on the 3rd.

Sunshine was above average with 211.6 hrs. (+8.25 hrs); the most was 13.1 hours on the 26th. There was 1 day without sunshine.

We had 0 air frost and 5 ground frosts.

Note: The average refers to the 30 year means 1991-2020.

April 2023: April was sunny but wet with below average temperatures.

Rainfall was 65.0 mm, which is 11.05 mm above average. We had 16 days with 0.2 mm or more of rain. The wettest day was the 12th with 9.7 mm which fell partly as hail and was part of an afternoon thunderstorm).

The average maximum and minimum temperatures were below average with 13.0 ºC (-0.41°C) and 4.0 °C (-0.47°C) respectively. The warmest day was the 29th which reached 17.7 ºC, and the coldest night was on the 4th when it dropped to -1.8 ºC.

Sunshine was above average with 176.3 hours (+4.24 hours); the most was 11.5 hours on the 4th and there were zero days without sunshine.

We had 1 air frost and 12 ground frosts of which 1 day dropped to below -6.0 °C.

Note: The average refers to the 30 year means 1991-2020.

March 2023: March was very wet with below average sunshine and slightly above average temperatures.

Rainfall was above average with 117.2 mm recorded, (+70.09 mm). We had 25 days with 0.2 mm or more of rain, and 7 days with more than 5 mm. The most recorded was 17.8 mm on the 31st. March 2023 is notable as the 4th wettest March in our records (since 1853).

The mean maximum temperature was below average at 9.8ºC (-0.45) and the mean minimum was above average at 3.7ºC (+0.82) respectively. The highest maximum temperature was 15.0ºC on the 30th and the lowest minimum was -4.0ºC on the 11th.

Sunshine was below average with 89.9 hrs (-38.49); the most recorded was 7.8 hours on the 2nd. There were 3 days without sunshine.

We had 5 air frosts and 11 ground frosts of which 3 days were below -6.0 °C.

Note: The average refers to the 30 year means 1991-2020.

February 2023: February was warm and especially dry, with above average sunshine.

Rainfall was below average with 5.7 mm (-51.29). We had 11 days with over 0.2 mm, and 0 days with more than 5.0 mm. The greatest rainfall was 2.0 mm on the 22nd. This February is the 6th driest on record since records began in 1853.

The mean maximum and mean minimum temperatures were above average with 9.6ºC (+2.04) and 2.2ºC (+0.69) respectively. The highest maximum was 14.5ºC on the 17th, and the lowest minimum was -5.8ºC on the 8th.

Sunshine was above average with 110.3 hrs. (+24.16). We had 4 days without any sunshine and the most was 8.0 hrs on the 13th.

We had 10 air frosts and 13 ground frosts of which 6 were below -6.0 º.

Note: The average refers to the 30 year means 1991-2020.

January 2023: January was warm, wet and especially sunny.

Rainfall was above average with 79.6 mm (+5.47 mm). We had 22 days with 0.2 mm or more of rain and 5 had more than 5.0 mm. The most on one day was 11.9 mm recorded on the 11th.

January’s mean maximum and minimum temperatures were above average with 8.0 ºC (+0.94 ºC) and 1.3 ºC (-0.30ºC) respectively. The warmest day reached 12.5 ºC on the 4th and the coldest temperature was -6.6 ºC on the 23rd.

Sunshine was well above average with 88.1 hours (+24.21 hours); the most was 6.8 hours on the 21st. We had 3 days with no sunshine. January was the 3rd sunniest in our records (began 1891).

We had 11 air frosts and 17 ground frosts of which 9 were below -6.0 °C.

Note: The average refers to the 30 year means 1991-2020.

Weather Summary for Harpenden, 2022: The year 2022 was warm, dry and very sunny.

Rainfall: 2022 had below average rainfall with 666.7 mm recorded; the annual average is 763.5 mm. It rained (0.2 mm or more) on 167 days. The most on one day was 30.7 mm on 23rd of October. The wettest month was November with 131.7mm. The driest month was July with 11.7 mm. Of the twelve months, eight had below average rainfall. Some of the recorded rainfall fell as snow and some as hail with hail being observed on the 23rd of November. There was very little snow of note during the first part of the year and not enough to settle. But in December there was a significant snowfall overnight on the 11th/12th and due to the freezing temperatures at that time, this remained for 7 days.

Temperature: The overall mean air temperature for the year was above average at 11.2 ºC (The annual average is 10.2 ºC). This makes 2022 the joint warmest year, with 2014, since our records began in 1878. The mean maximum air temperature was above average at 15.5 ºC (+1.5 ºC). The mean minimum air temperature was above average at 6.9 ºC (+0.5 ºC). The hottest day was the 19th of July reaching 38.4 ºC which is the highest maximum temperature recorded at Rothamsted (since 1878). The coldest night was the 15th of December which dropped to -9.0 ºC.

Sunshine: 2022 was a very sunny year with 1912.5 hours of sunshine (259.9 hours above the annual average). This makes 2022 the second sunniest year on record with 2020 being the sunniest. July was the ‘sunniest’ month with 254.5 hours. Of the twelve months only May and September had below average sunshine.

We had 36 air frosts and 109 ground frosts, of which 16 were below -6 ºC.

Note: The average refers to the 30 year means 1991-2020.

December 2022: December was relatively cool, dry and sunny. There was a period of freezing temperatures from the 7th to the 19th along with snow fall on the night of the 11th which settled and lasted for 7 days.

Rainfall was 67.9 mm, which is 7.7 mm below average. We had 16 days where at least 0.2 mm of rain was recorded, 6 of these with at least 5 mm. The most was 10.7 mm on the 31st.

December had below average mean maximum and minimum temperatures with 6.4 ºC (-0.97) and 0.1ºC (-1.90) respectively. The highest maximum temperature was 12.6 ºC on the 30th and the lowest minimum was -9 ºC on the 15th.

Sunshine was 10.58 hrs above average with 71.4 hrs. The most sunshine was 6 hours on the 8th. We had 8 days with no sunshine recorded.

We had 13 air frosts and 21 ground frosts, of which 4 were below -6 °C.

Note: The average refers to the 30 year means 1991-2020.

November 2022: November was sunny, wet and warm.

Rainfall was 131.7 mm which is 50.46 mm above average. We had 24 days with 0.2 mm or more of rain, and 7 days with over 5 mm. The most was 24.6 mm on the 2nd. Hail was observed on morning of 23rd.

The maximum and minimum mean air temperatures were both above average with 11.8 ºC (+1.69 ºC) and 6.5 ºC (+2.24 ºC) respectively. The warmest day reached 15.4 ºC on the 12th and the lowest minimum was 1.1 ºC on the 21st.

Sunshine was above average with 77.0 hours (+4.77 hours); the most was 6.6 hours on the 4th. There were 4 days without sunshine.

There were 5 ground frosts.

Note: The average refers to the 30 year means 1991-2020.

October 2022: October was particularly warm and sunny, with above average rainfall. Most of the rain fell during the second half of the month with the wettest day being accompanied by a thunderstorm on the night of the 23rd.

Rainfall was 101.0 mm which is 19.68 mm above average. We had 18 days with 0.2 mm or more of rain and 7 with over 5.0 mm. The greatest fall was 30.7 mm which fell on the 23rd.

The mean maximum and minimum temperatures were above average with 16.8 ºC (+2.51) and 9.2 ºC (+1.62) respectively. The highest temperature was 21.0 ºC on the 29th and the lowest was 2.6 ºC on the 11th. It was the 5th warmest October since our temperature records began in 1878.

Sunshine was above average with 147.6 hrs (average for October is 113.0); the most was 9.3 hours on the 8th. There were no days without sunshine and October ranked as 7th sunniest since our records began in 1890.

There were 5 ground frosts.

Note: The average refers to the 30 year means 1991-2020.

September 2022: The month of September was relatively cloudy and wet with close to average air temperatures.

Rainfall was 77.9 mm, which is 20.14 mm above average. We had 16 days with 0.2 mm or more of rain and 5 days with over 5 mm. The most was 14.3 mm on the 30th.

The mean maximum temperature was below average at 18.5 ºC (-0.05 ºC) and the mean minimum was above average at 10.6 ºC (+0.42 ºC). The highest (daytime) temperature was 24.7 ºC on the 12th. The lowest (night) temperature was 4.5 ºC on the 29th.

Sunshine was 127 hrs which is 23.73 hrs below average. There was sunshine on every day and the most recorded was 11.1 hours on the 17th.

There were 4 ground frosts recordeds.

Note: The average refers to the 30 year means 1991-2020.

August 2022: August was mainly dry, sunny and the warmest August on record.

Rainfall was below average with 41.4 mm (-30.58 mm). We had 5 days with 0.2 mm or more of rain, of which 2 days had more than 5.0 mm; the most was 21.6 mm on the 24th.

The mean maximum and minimum air temperatures were above average with 25.2 ºC (+3.55 ºC), highest on record, and 13.9 ºC (+1.62 ºC) respectively. The highest temperature was 32.3 ºC on the 13th. The lowest temperature was 8.9 ºC on the 7th.

Sunshine was above average with 245.6 hours (+56.19 hours). There were 0 days without sun and the sunniest day was the 7th with 13.3 hours.

There were no frosts.

Note: The average refers to the 30 year means 1991-2020.

July 2022: The month of July was very warm, dry and sunny.

Rainfall was 11.7 mm, which is 43.74 mm below average. We had 5 days with 0.2 mm or more of rain with 1 day having more than 5 mm. The greatest rainfall was 5.5 mm recorded on the 20th.

The average maximum and minimum air temperatures were above average at 24.9 ºC (+2.93 ºC) and 13.1 ºC (+0.79 ºC) respectively. The hottest day was the 19th reaching 38.4 ºC. This is the highest maximum temperature recorded since records began in 1878. Previous record was 36.7 ºC on 25th July 2019. The lowest minimum air temperature was 8.3 ºC on the 5th.

Sunshine was above average with 254.5 hrs (+47.68 hours). The most was 14.2 hours on the 10th and there was 0 days where no sunshine was recorded.

We had no air or ground frosts.

Note: The average refers to the 30 year means 1991-2020.

June 2022: June was warmer, drier and sunnier than average.

Rainfall was 43.8 mm, which is 10.99 mm below average. We had 13 days with 0.2 mm or more of rain, of which 3 days had more than 5.0 mm. The most rainfall in a single day was 19.2 mm collected on the 4th.

The mean maximum air temperature was above average at 20.8 ºC (+1.29 ºC). The mean minimum air temperature was below average at 10.0 ºC (-0.20 ºC). The hottest day reached 30.7 ºC on the 17th. The coolest night was 5.1 ºC on the 2nd.

Sunshine was 253.6 hours, which is 47.85 hours above average. There was 1 day without sun.

There were 0 air frosts and 2 ground frosts.

Note: The average refers to the 30 year means 1991-2020.

May 2022: May was warmer and drier than average with just below average sunshine.

Rainfall was 33.9 mm, which is 19.33 mm below average. We had 14 days with 0.2 mm or more of rain, of which 1 day had more than 1.0 mm. The greatest fall of rain was 5.3 mm on the 30th of May.

The average maximum and minimum temperatures were above average at 17.9 ºC (+1.42 ºC) and 8.4 ºC (+1.06 ºC) respectively. The highest (max) temperature was 24.6 ºC on the 17th and the lowest (min) temperature was 3.3ºC on the night of the 9th.

Sunshine was below average with 195.1 hrs. (-8.24 hrs); the most was 12.8 hours on the 27th. There were 0 days without sunshine.

We had 0 air frost and 4 ground frosts.

Note: The average refers to the 30 year means 1991-2020.

April 2022: April was sunny and dry along with close to average temperatures.

Rainfall was 20.8 mm, which is 33.19 mm below average. We had 8 days with 0.2 mm or more of rain. The wettest day was the 6th with 9.3 mm.

The average maximum temperature was above average at 14.2 ºC (+0.78ºC); while the average minimum was below average at 4.1 ºC (-0.41ºC). The warmest day was the 15th which reached 21.2 ºC, and the coldest night was on the 3rd when it dropped to -3.0ºC.

Sunshine was above average with 197.5 hours (+25.44 hours); the most was 12.0 hours on the 21st and there were 2 days without sunshine..

We had 5 air frosts and 15 ground frosts.

Note: The average refers to the 30 year means 1991-2020.

March 2022: March was especially sunny along with above average temperatures and below average rainfall. There were wintery showers during a cold spell at the end of the month.

Rainfall was below average with 34.1 mm recorded, (-12.93 mm). We had 13 days with 0.2 mm or more of rain, and 2 days with more than 5 mm. The most recorded was 14.7 mm on the 16th. There were snow and hail showers throughout the 31st.

The mean maximum and minimum temperatures were above average with 11.8ºC (+1.50) and 3.4ºC (+0.58) respectively. The highest maximum temperature was 18.7ºC on the 23rdand the lowest minimum was -2.0ºC on the 21st.

Sunshine was above average with 167.0 hrs (+38.58); the most recorded was 11 hours on the 26th. There were 5 days without sunshine.

We had 3 air frosts and 16 ground frosts.

Note: The average refers to the 30 year means 1991-2020.

February 2022: February was relatively warm and wet and had above average sunshine.

Rainfall was above average with 79.0 mm (+22.04). We had 19 days with over 0.2 mm, and 7 days with more than 5.0 mm. The greatest rainfall was 13.9 mm on the 13th. Precipitation fell as sleet and snow on the 4th and there were sleet, snow, and hail showers on 24th.

The mean maximum and the mean minimum temperatures were above average with 9.9 ºC (+2.36) and 3.0 ºC (+1.50) respectively. The lowest minimum was -0.6 ºC on the 26th, and the highest maximum was 14.1 ºC on the 24th. February 2022 was the 8th warmest February since our records began in 1878.

Sunshine was above average with 90.0 hrs. (+3.82). We had 3 days without any sunshine and the most was 9.3 hrs on the 27th.

We had 2 air frosts and 14 ground frosts of which 2 were below -6.0 ºC.

Note: The average refers to the 30 year means 1991-2020.

January 2022: January was especially dry and sunny with close to the average temperatures.

Rainfall was well below average with 23.4 mm (-50.69 mm). We had 16 days with 0.2 mm or more of rain and 2 had more than 5.0 mm. The most on one day was 6.5 mm recorded on the 2nd.

The mean maximum temperature was above average at 7.6 ºC (+0.53 ºC) and the minimum was below average at 0.8 ºC (-0.74 ºC). The warmest day reached 13.6 ºC on the 1st and the coldest temperature was -5.0 ºC on the 6th.

Sunshine was well above average with 86.3 hours (+22.40 hours); the most was 7.3 hours on the 31st. We had 7 days with no sunshine. January was the 5th sunniest in our records (began 1891).

We had 13 air frosts and 19 ground frosts of which 7 were below -6.0 ºC.

Note: The average refers to the 30 year means 1991-2020.

December 2021: December was warm for the time of year with above average rainfall and below average sunshine.

Rainfall was 76.2 mm, which is 0.58 mm above average. We had 24 days where at least 0.2 mm of rain was recorded, 5 of these with at least 5 mm. The most was 20.8 mm on the 24h.

There were above average mean maximum and minimum temperatures. The mean maximum was 8.6 ºC (+1.16) and the mean minimum was 3.9ºC (+1.94). The highest maximum temperature was 14.2ºC on the 29th and the lowest minimum was -2.5ºC on the 22nd.

Sunshine was below average with 23.5 hrs which is 37.31 hrs below average. The most sunshine was 5.8 hours on the 2nd. We had 14 days with no sunshine recorded.

We had 5 air frosts and 9 ground frosts.

Note: The average refers to the 30 year means 1991-2020.

November 2021: November was sunny, cold and noticeably dry.

Rainfall was 19.2 mm which is 62.02 mm below average. We had 16 days with 0.2 mm or more of rain, and 1 day with over 5 mm. The most was 6.7 mm on the 26th. Precipitation fell as snow on 28th.

The maximum and minimum mean air temperatures were both below average with 10.0 ºC (-0.07 ºC) and 3.9 ºC (-0.37 ºC) respectively. The warmest day reached 14.7 ºC on the 9th and the lowest minimum was -2.6 ºC on the 29th.

Sunshine was above average with 82.1 hours (+9.89 hours); the most was 7.7 hours on the 1st. There were 5 days without sunshine.

There were four ground frosts.

Note: The average refers to the 30 year means 1991-2020.

October 2021: October was relatively cloudy, mild and wet for the time of year.

Rainfall was 104.8 mm which is 23.51 mm above average. We had 17 days with 0.2 mm or more of rain and 6 with over 5.0 mm. The greatest rainfall was 23.0 mm which fell on the 20th.

The October mean maximum and minimum temperatures were above average with 15.2 ºC (+0.94) and 8.6 ºC (+1.01) respectively. The highest temperature was 19.3 ºC on the 19th and the lowest was 3.7 ºC on the 22nd.

Sunshine was below average with 95.1 hrs (-17.97 hours); the most was 7.9 hours on the 6th. There was 1 day without sunshine.

There were four ground frosts.

Note: The average refers to the 30 year means 1991-2020.

September 2021: The month of September was warm and dull with below average rainfall.

Rainfall was 54.1 mm, which is 3.60 mm below average. We had 11 days with 0.2 mm or more of rain and 4 days with over 5 mm. The most was 24.2 mm on the 28th.

The mean maximum The mean maximum and minimum temperatures were above average at 20.6 ºC (+2.08 ºC) and 11.5 ºC (+1.32 ºC) respectively. The highest (daytime) temperature was 27.9 ºC on the 7th. The lowest (night) temperature was 4.6 ºC on the 30th.

Sunshine was 136.2 hrs which is 14.46 hrs below average. There was 1 day without sunshine and the most recorded was 11.7 hours on the 7th.

There were no frosts.

Note: The average refers to the 30 year means 1991-2020.

August 2021: August was cool, dry and dull with below average temperature, rainfall and sunshine.

Rainfall was below average with 37.0 mm (-34.99 mm). We had 13 days with 0.2 mm or more of rain, of which 3 days had more than 5.0 mm; the most was 16.8 mm on the 21st.

The mean maximum air temperature was below average with 19.9 ºC (-1.69 ºC) and the mean minimum air temperature was just above average with 12.3 ºC (+0.02 ºC). The highest temperature was 23.3 ºC on the 14th. The lowest temperature was 8.1 ºC on the 29th.

Sunshine was below average with 114.2 hours (-75.21 hours). There were two days without sun and the sunniest day was the 4th with 9.4 hours.

There were no frosts.

Note: The average refers to the 30 year means 1991-2020.

July 2021: July 2021 was warm, relatively dry and dull.

Rainfall was 51.0 mm, which is 4.46 mm below average. We had 17 days with 0.2 mm or more of rain with 2 days having more than 5 mm. The greatest rainfall was 21.4 mm recorded on the 5th.

Sunshine was below average with 195.6 hrs (-11.18 hours). The most was 14.4 hours on the 16th and there was 0 days where no sunshine was recorded.

The average maximum air temperature was 22.3 ºC (+0.29 ºC) and the average minimum air temperature was 13.4 ºC (+1.04 ºC). The warmest day reached 29.5 ºC on the 20th. The lowest minimum air temperature was 10.0 ºC on the 16th.

There were no frosts.

Note: The average refers to the 30 year means 1991-2020.

June 2021: June 2021 was warm, wet and relatively cloudy.

Rainfall was 77.6 mm, which is 22.78 mm above average. We had 11 days with 0.2 mm or more of rain, of which 5 days had more than 5.0 mm. The most rainfall in a single day was 23.6 mm collected on the 18th.

Sunshine was 184.7 hours, which is 21.09 below average.

The mean maximum and minimum temperatures were both above average with 20.3ºC (+0.77ºC) and 11.8 ºC (+1.62ºC) respectively. The hottest day reached 26.2ºC on the 13th. The coolest night dropped to 5.1ºC on the 23rd. The June 2021 average air temperature was the 8th warmest in our records (started 1878).

There were no frosts.

Note: The average refers to the 30 year means 1991-2020.

May 2021: May was a cold, dull and wet month with below average temperatures and sunshine hours, and above average rainfall.

Rainfall was 94.4 mm, which is 41.14 mm above average. We had 24 days with 0.2 mm or more of rain, of which 9 days had more than 1.0 mm. The greatest fall of rain was 11.2 mm on the 21st of May.

Sunshine was below average with 150.4 hrs. (-52.92 hrs); the most was 10.1 hours on the 31st. There was one day without sunshine.

The average maximum and minimum temperatures were below average at 14.7ºC (-1.78ºC) and 6.2ºC (-1.10ºC). The highest (max) temperature was 22.3 ºC on the 31st and the lowest (min) temperature was 0.2ºC on the night of the 6th.

We had 0 air frosts and 10 ground frosts.

Note: The average refers to the 30 year means 1991-2020.

April 2021: April was sunny, cold, and mainly dry.

Rainfall was 1.6 mm which is 52.40 mm below average. We had 4 days with 0.2 mm or more of rain. The wettest day was the 9th with 1.0 mm. April was the driest since records began in 1853.

Sunshine was above average with 215.8 hours (+43.79 hours); the most was 12.9 hours on the 22nd and there was only 1 day without sunshine.

The average maximum and minimum temperatures were below average at 11.5ºC (-1.84ºC) and 1.1ºC (-3.36ºC). The warmest day was the 19th which reached 16.2ºC, and the coldest night was on the 7th when it dropped to -3.0ºC.

We had 11 air frosts and 22 ground frosts.

Note: The average refers to the 30 year means 1991-2020.

March 2021: March was relatively warm and cloudy with below average rainfall.

Rainfall was below average with 27.6 mm recorded, (-19.47 mm). We had 13 days with 0.2 mm or more of rain, and 1 day with more than 5 mm. The most recorded was 5.0 mm on the 10th.

Sunshine was below average with 112.0 hrs (-16.36); the most recorded was 10.9 hours on the 30th. There were 2 days without sunshine.

The mean maximum and minimum temperatures were above average with 10.7ºC (+0.42) and 3.5ºC (+0.62) respectively. The highest maximum temperature was 22.5ºC on the 30th and the lowest minimum was -1ºC on the 6th.

We had 1 air frost and 18 ground frosts.

Note: The average refers to the 30 year means 1991-2020.

February 2021: February was warm with below average sunshine and rain with some snow.

Rainfall was below average with 45.8 mm (-11.15 mm). We had 15 days with over 0.2 mm, and 4 days with more than 5.0 mm. The greatest rainfall was 9.0 mm on the 4th. Precipitation fell as snow on 8th with a very slight flurry on afternoon of 10th.

Sunshine was below average with 80.8 hrs. (-5.38 hrs). We had 3 days without any sunshine and the most was 9.1 hrs on the 26th.

The mean maximum and the mean minimum temperatures were above average with 8.1 ºC (+0.56ºC) and 2.2ºC (+0.73ºC) respectively. The lowest minimum was -4.9ºC on the 11th, and the highest maximum was 16.0ºC on the 24th.

We had 8 air frosts and 14 ground frosts.

Note: The average refers to the 30 year means 1991-2020.

January 2021: January was cold, wet and had below average sunshine.

Rainfall was above average with 113.6 mm (+39.48 mm). We had 23 days with 0.2 mm or more of rain and 10 had more than 5.0 mm. The most on one day was 25.6 mm on the 13th. Snow fell and settled on 24th.

Sunshine was below average with 52.0 hours (-11.91 hours); the most was 7.0 hours on the 25th. We had 9 days with no sunshine.

January’s mean maximum and minimum temperatures were below average at 5.8ºC (-1.20ºC) and 0.4ºC (-1.22ºC) respectively. The highest day temperature was 11.7ºC on the 28th and the lowest minimum was -4.9ºC on the 25th.

We had 17 air frosts and 18 ground frosts.

Note: The average refers to the 30 year means 1991-2020.

Previous Years

Key References

2021

  • Addy, J. W. G. , Ellis, R. H. , Macdonald, A. J. , Semenov, M. A. and Mead, A.(2021) "The impact of weather and increased atmospheric CO2 from 1892 to 2016 on simulated yields of UK wheat", J. R. Soc. Interface, 18, 20210250
    DOI: 10.1098/rsif.2021.0250

2020

  • Addy, J. W. G. , Ellis, R. H. , Macdonald, A. J. , Semenov, M. A. and Mead, A.(2020) "Investigating the effects of inter-annual weather variation (1968-2016) on the functional response of cereal grain yield to applied nitrogen, using data from the Rothamsted Long-Term Experiments", Agricultural and Forest Meteorology, 284, 107898
    DOI: 10.1016/j.agrformet.2019.107898

2018

  • Macdonald, A. , Poulton, P. , Clark, I. , Scott, T. , Glendining, M. , Perryman, S. , Storkey, J. , Bell, J. , Shield, I. , Mcmillan, V. and Hawkins, J.(2018) "Guide to the Classical and Other Long-term experiments, Datasets and Sample Archive. Rothamsted Research", , 57 pp.
    DOI: 10.23637/ROTHAMSTED-LONG-TERM-EXPERIMENTS-GUIDE-2018

2015

  • Scott, T.(2015) "The U.K. Environmental Change Network Rothamsted. Physical and Atmospheric Measurements. The first 20 Years. Lawes Agricultural Trust Ltd.", , 32pp.
    DOI: 10.23637/ecn-rothamsted-booklet-2015

1974

Rothamsted
BBSRC

For further information and assistance, please contact the e-RA curators, Sarah Perryman and Margaret Glendining using the e-RA email address: era@rothamsted.ac.uk