Daily Report for 20th January 2021

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Measure Value (anomaly) Time Month cumul. Record High Record Low
Minimum Temperature 7.6 °C (+5.3) 23:58 1.3 °C (-1.1) 7.6 °C (+5.3), 2021 -3.6 °C (-5.9), 2015
Maximum Temperature 10.4 °C (+3.4) 00:25 6.1 °C (-0.9) 10.4 °C (+3.4), 2021 -0.3 °C (-7.3), 2013
Mean Temperature 9.8 °C (+4.3) 3.8 °C (-1.0) 9.8 °C, 2021 -1.0 °C, 2013
Minimum Humidity 84% 21:17 84% 87%, 2010 45%, 2017
Maximum Humidity 93% 23:28 94% 98%, 2013 76%, 2017
Mean Humidity 90% 90% 94%, 2014 67%, 2017
Minimum Pressure 974 hPa 23:16 1014 hPa 1045 hPa, 2020 974 hPa, 2021
Maximum Pressure 997 hPa 00:02 1022 hPa 1050 hPa, 2020 996 hPa, 2009
Mean Pressure 988 hPa 1018 hPa 1048 hPa, 2020 988 hPa, 2021
Mean Wind Speed 13.7 mph (+8.5) 4.7 mph (-0.5) 13.7 mph, 2021 0.4 mph, 2014
Maximum Wind Speed 24.7 mph 23:29 12.4 mph 24.7 mph, 2021 4.0 mph, 2016
Maximum Gust 37.6 mph 23:22 19.5 mph 37.6 mph, 2021 4.9 mph, 2016
Mean Wind Direction SW
Rainfall 2.6 mm 48.5 mm (137%) 8.0 mm, 2013
Maximum Hourly Rain 1.9 mm 23:42 2.2 mm, 2018
Maximum 10-min Rain 1.2 mm 23:35 1.2 mm, 2021
Maximum Rain Rate 14 mm/h 23:29 14 mm/h, 2021
Minimum Dew Point 5.7 °C 23:58 -0.0 °C 5.7 °C, 2021 -5.4 °C, 2016
Maximum Dew Point 8.9 °C 03:47 4.6 °C 8.9 °C, 2021 -1.9 °C, 2017
Mean Dew Point 8.2 °C 2.4 °C 8.2 °C, 2021 -3.3 °C, 2017
Measure Value Time Month cumul. Record High Record Low
Night Minimum (21-09) * 9.8 °C * 08:54 2.2 °C 9.8 °C, 2021 -3.6 °C, 2015
Day Maximum (09-21) * 10.3 °C * 10:46 5.8 °C 10.3 °C, 2021 -0.3 °C, 2013
Max 10m Temp Rise 0.3 °C 20:36 0.3 °C 0.7 °C, 2014 0.1 °C, 2010
Max 1hr Temp Rise 0.7 °C 21:06 1.0 °C 2.6 °C, 2014 0.1 °C, 2010
Max 1hr Hum Rise 6% 22:06 4% 8%, 2017 1%, 2010
Max 10m Temp Fall 0.8 °C 23:40 0.4 °C 0.8 °C, 2021 0.1 °C, 2010
Max 1hr Temp Fall 1.7 °C 23:58 1.1 °C 1.8 °C, 2014 0.3 °C, 2010
Max 1hr Hum Fall 5% 18:59 4% 10%, 2017 2%, 2013
Max 10m Wind Speed 17.8 mph 22:19 9.8 mph 17.8 mph, 2021 3.0 mph, 2016
Minimum Feels-like 2.9 °C 23:55 -2.9 °C 2.9 °C, 2021 -8.4 °C, 2013
Maximum Feels-like 11.1 °C 00:08 5.8 °C 11.1 °C, 2021 -0.5 °C, 2013
Mean Feels-like 8.0 °C 1.7 °C 8.0 °C, 2021 -4.4 °C, 2013
Air-frost Hrs 0 hrs 3 hrs 24 hrs, 2013 0 hrs, 2010
Measure Value (anomaly) Month cumul. Record High Record Low
Temperature Range 2.8 °C (-1.9) 4.8 °C (+0.2) 7.8 °C (+3.1), 2015 1.4 °C (-3.3), 2010
Humidity Range 9% 10% 31%, 2017 8%, 2010
Pressure Range 23 hPa 8 hPa 23 hPa, 2021 3 hPa, 2011
Measure Value [% of max] Month cumul. Record High Record Low
Sun Hours 0 [0%]22 hrs (58%) [15%] 7.7 [101%], 2017 0 [0%], 2010
Wet Hours 3
[Mean rain rate: 0.9 mm/h]
54 hrs (124%) [11%] 13, 2013 , 2009
Cloud Cover Overcast
Events None
Comments rn
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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Webcam Summary of Cloud Conditions

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