Daily Report for 21st January 2021

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Measure Value (anomaly) Time Month cumul. Record High Record Low
Minimum Temperature 3.9 °C (+1.6) 05:16 1.5 °C (-1.0) 7.1 °C (+4.8), 2012 -2.6 °C (-4.9), 2019
Maximum Temperature 8.3 °C (+1.3) 13:54 6.2 °C (-0.8) 12.3 °C (+5.3), 2012 1.4 °C (-5.6), 2013
Mean Temperature 6.1 °C (+1.5) 3.9 °C (-0.9) 10.0 °C, 2012 -0.0 °C, 2013
Minimum Humidity 72% 13:40 83% 91%, 2018 47%, 2017
Maximum Humidity 88% 00:00 94% 98%, 2013 80%, 2017
Mean Humidity 80% 90% 95%, 2018 66%, 2017
Minimum Pressure 976 hPa 00:01 1012 hPa 1040 hPa, 2020 976 hPa, 2021
Maximum Pressure 988 hPa 23:55 1020 hPa 1045 hPa, 2020 988 hPa, 2021
Mean Pressure 986 hPa 1016 hPa 1042 hPa, 2020 986 hPa, 2021
Mean Wind Speed 7.9 mph (+2.7) 4.8 mph (-0.4) 8.3 mph, 2012 1.5 mph, 2017
Maximum Wind Speed 19.2 mph 10:53 12.7 mph 19.2 mph, 2012 5.8 mph, 2020
Maximum Gust 34.2 mph 02:18 20.2 mph 34.2 mph, 2021 8.1 mph, 2013
Mean Wind Direction WSW
Rainfall 0.0 mm 48.5 mm (130%) 12.3 mm, 2018
Maximum Hourly Rain n/a 3.1, 2018
Maximum 10-min Rain n/a 0.7, 2018
Maximum Rain Rate n/a 4.4, 2018
Minimum Dew Point 1.3 °C 03:48 0.1 °C 1.3 °C, 2021 -8.5 °C, 2017
Maximum Dew Point 5.6 °C 00:00 4.6 °C 9.3 °C, 2018 -1.9 °C, 2017
Mean Dew Point 2.9 °C 2.4 °C 4.8 °C, 2012 -5.1 °C, 2017
Measure Value Time Month cumul. Record High Record Low
Night Minimum (21-09) 3.9 °C 05:08 2.2 °C 8.5 °C, 2012 -2.6 °C, 2019
Day Maximum (09-21) 8.3 °C 13:55 5.9 °C 12.3 °C, 2012 1.4 °C, 2013
Max 10m Temp Rise 0.3 °C 07:04 0.3 °C 0.8 °C, 2016 0.2 °C, 2011
Max 1hr Temp Rise 1.2 °C 09:27 1.0 °C 2.4 °C, 2020 0.4 °C, 2015
Max 1hr Hum Rise 4% 04:31 4% 7%, 2012 2%, 2014
Max 10m Temp Fall 0.4 °C 00:10 0.4 °C 0.5 °C, 2020 0.2 °C, 2010
Max 1hr Temp Fall 1.4 °C 01:01 1.2 °C 2.3 °C, 2020 0.5 °C, 2019
Max 1hr Hum Fall 5% 10:20 4% 22%, 2017 2%, 2015
Max 10m Wind Speed 14.7 mph 11:20 10.0 mph 14.7 mph, 2021 4.4 mph, 2020
Minimum Feels-like -2.1 °C 04:15 -2.9 °C 4.4 °C, 2012 -4.5 °C, 2017
Maximum Feels-like 7.7 °C 16:04 5.9 °C 12.5 °C, 2012 1.3 °C, 2013
Mean Feels-like 2.9 °C 1.8 °C 9.3 °C, 2012 -1.1 °C, 2013
Air-frost Hrs 0 hrs 3 hrs 13 hrs, 2013 0 hrs, 2010
Measure Value (anomaly) Month cumul. Record High Record Low
Temperature Range 4.4 °C (-0.3) 4.8 °C (+0.2) 9.1 °C (+4.4), 2018 2.8 °C (-1.9), 2015
Humidity Range 16% 11% 44%, 2009 7%, 2018
Pressure Range 12 hPa 8 hPa 16 hPa, 2019 2 hPa, 2011
Measure Value [% of max] Month cumul. Record High Record Low
Sun Hours 3 [39%]25 hrs (63%) [16%] 7.7 [101%], 2017 0 [0%], 2015
Wet Hours 054 hrs (119%) [11%] 10, 2018 , 2009
Cloud Cover am: Sunny
pm: Overcast
Events None
Comments -
Extra Comments
Issues None known
Observer Absent? Yes - observations may be unreliable
Pond Temperature (Heath) 4.5 °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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