Daily Report for 21st May 2020

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Measure Value (anomaly) Time Month cumul. Record High Record Low
Minimum Temperature 13.4 °C (+4.5) 05:17 7.1 °C (-0.6) 13.5 °C (+4.6), 2016 5.5 °C (-3.4), 2015
Maximum Temperature 27.4 °C (+10.1) 16:27 18.9 °C (+2.7) 27.4 °C (+10.1), 2020 12.7 °C (-4.6), 2021
Mean Temperature 21.4 °C (+7.3) 13.4 °C (+1.1) 21.4 °C, 2020 11.3 °C, 2021
Minimum Humidity 28% 15:34 43% 71%, 2012 28%, 2020
Maximum Humidity 86% 05:49 85% 93%, 2012 81%, 2015
Mean Humidity 55% 64% 83%, 2012 55%, 2011
Minimum Pressure 1017 hPa 23:59 1018 hPa 1029 hPa, 2010 996 hPa, 2021
Maximum Pressure 1022 hPa 00:36 1023 hPa 1032 hPa, 2010 1002 hPa, 2021
Mean Pressure 1020 hPa 1020 hPa 1030 hPa, 2010 998 hPa, 2021
Mean Wind Speed 2.5 mph (-2.2) 4.2 mph (-0.5) 13.9 mph, 2021 2.2 mph, 2018
Maximum Wind Speed 10.9 mph 19:59 12.5 mph 23.5 mph, 2021 8.4 mph, 2010
Maximum Gust 17.3 mph 20:04 19.1 mph 42.2 mph, 2021 12.0 mph, 2010
Mean Wind Direction SW
Rainfall 0.0 mm 5.3 mm (16%) 2.4 mm, 2021
Maximum Hourly Rain n/a 0.7, 2021
Maximum 10-min Rain n/a 0.5, 2021
Maximum Rain Rate n/a 2.4, 2021
Minimum Dew Point 6.8 °C 23:43 3.2 °C 9.5 °C, 2010 1.2 °C, 2015
Maximum Dew Point 15.5 °C 12:22 8.8 °C 15.5 °C, 2020 7.6 °C, 2015
Mean Dew Point 11.3 °C 6.2 °C 12.2 °C, 2010 3.8 °C, 2015
Measure Value Time Month cumul. Record High Record Low
Night Minimum (21-09) 13.4 °C 05:10 7.6 °C 13.5 °C, 2016 5.5 °C, 2015
Day Maximum (09-21) 27.4 °C 16:53 18.9 °C 27.4 °C, 2020 12.7 °C, 2021
Max 10m Temp Rise 0.8 °C 08:07 0.7 °C 1.7 °C, 2010 0.4 °C, 2012
Max 1hr Temp Rise 3.2 °C 08:56 2.9 °C 5.7 °C, 2011 1.0 °C, 2016
Max 1hr Hum Rise 10% 02:13 10% 14%, 2018 4%, 2012
Max 10m Temp Fall 0.6 °C 01:23 0.7 °C 1.0 °C, 2010 0.2 °C, 2012
Max 1hr Temp Fall 2.4 °C 02:13 2.2 °C 2.4 °C, 2020 0.7 °C, 2012
Max 1hr Hum Fall 14% 13:46 14% 25%, 2010 5%, 2012
Max 10m Wind Speed 8.5 mph 20:05 9.1 mph 18.3 mph, 2021 6.6 mph, 2018
Minimum Feels-like 15.1 °C 04:53 5.2 °C 15.1 °C, 2020 3.0 °C, 2015
Maximum Feels-like 29.8 °C 13:38 19.8 °C 29.8 °C, 2020 13.1 °C, 2021
Mean Feels-like 23.3 °C 13.3 °C 23.3 °C, 2020 11.6 °C, 2021
Air-frost Hrs 0 hrs 0 hrs 0 hrs, 2009 0 hrs, 2009
Measure Value (anomaly) Month cumul. Record High Record Low
Temperature Range 14.0 °C (+5.6) 11.8 °C (+3.3) 14.6 °C (+6.2), 2015 2.8 °C (-5.6), 2021
Humidity Range 58% 43% 58%, 2020 17%, 2013
Pressure Range 5 hPa 5 hPa 10 hPa, 2014 2 hPa, 2012
Measure Value [% of max] Month cumul. Record High Record Low
Sun Hours 12 [83%]196 hrs (165%) [67%] 13.5 [94%], 2011 0 [0%], 2021
Wet Hours 02 hrs (7%) [0.4%] 5, 2021 0, 2009
Cloud Cover Sunny with periods of Hazy
Events None
Comments -
Extra Comments
Issues None known
Observer Absent? Yes - observations may be unreliable
Pond Temperature (Heath) 5.0 °C
Notes
Times of extremes are computed using the midpoint of the longest continuous period at that extreme value.
Cumulative anomalies are reported according to the expected value for the month-to-date rather than month-end.
Sun hrs are initially pulled from the official weather station at Heathrow, and later adjusted by hand to reflect local conditions based on webcam observations. Wet hrs are dervied algorithmically from rainfall data, though may be adjusted manually. Cloud cover and Events are manually reported, often with multi-week delays.
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Daily Graph of Conditions

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Webcam Summary of Cloud Conditions

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