Daily Report for 27th September 2021

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Measure Value (anomaly) Time Month cumul. Record High Record Low
Minimum Temperature 12.2 °C (+1.8) 23:57 13.4 °C (+2.2) 13.3 °C (+2.9), 2017 8.7 °C (-1.7), 2015
Maximum Temperature 17.6 °C (+0.5) 16:29 21.4 °C (+2.4) 23.6 °C (+6.5), 2018 13.2 °C (-3.9), 2020
Mean Temperature 15.9 °C (+1.2) 17.3 °C (+2.3) 17.0 °C, 2018 11.3 °C, 2020
Minimum Humidity 56% 17:06 66% 80%, 2010 29%, 2018
Maximum Humidity 93% 08:45 93% 98%, 2010 81%, 2020
Mean Humidity 78% 81% 91%, 2010 62%, 2018
Minimum Pressure 1004 hPa 08:33 1017 hPa 1031 hPa, 2015 999 hPa, 2012
Maximum Pressure 1020 hPa 23:29 1022 hPa 1036 hPa, 2015 1008 hPa, 2019
Mean Pressure 1012 hPa 1019 hPa 1033 hPa, 2015 1005 hPa, 2019
Mean Wind Speed 7.0 mph (+3.1) 2.5 mph (-1.4) 7.1 mph, 2019 0.8 mph, 2014
Maximum Wind Speed 17.1 mph 08:48 9.4 mph 20.8 mph, 2016 4.9 mph, 2014
Maximum Gust 27.4 mph 08:52 14.6 mph 33.9 mph, 2016 7.8 mph, 2014
Mean Wind Direction SW
Rainfall 2.6 mm 29.4 mm (67%) 13.9 mm, 2017
Maximum Hourly Rain 1.4 mm 07:56 4.8 mm, 2017
Maximum 10-min Rain 0.7 mm 09:15 3.5 mm, 2019
Maximum Rain Rate 7 mm/h 09:13 92 mm/h, 2019
Minimum Dew Point 8.3 °C 18:27 11.4 °C 12.5 °C, 2017 4.3 °C, 2018
Maximum Dew Point 15.6 °C 08:45 16.1 °C 15.8 °C, 2011 8.9 °C, 2020
Mean Dew Point 11.8 °C 13.9 °C 13.6 °C, 2011 7.5 °C, 2020
Measure Value Time Month cumul. Record High Record Low
Night Minimum (21-09) * 16.1 °C * 00:29 13.8 °C 16.1 °C, 2021 8.7 °C, 2015
Day Maximum (09-21) 17.6 °C 16:29 21.4 °C 23.6 °C, 2018 13.2 °C, 2020
Max 10m Temp Rise 0.5 °C 13:58 0.6 °C 0.8 °C, 2018 0.3 °C, 2011
Max 1hr Temp Rise 1.3 °C 14:22 2.2 °C 3.3 °C, 2018 1.3 °C, 2011
Max 1hr Hum Rise 9% 20:10 7% 17%, 2012 2%, 2020
Max 10m Temp Fall 1.2 °C 09:21 0.5 °C 1.2 °C, 2021 0.1 °C, 2010
Max 1hr Temp Fall 2.1 °C 10:04 1.6 °C 3.1 °C, 2018 0.4 °C, 2010
Max 1hr Hum Fall 10% 10:47 9% 19%, 2018 4%, 2020
Max 10m Wind Speed 13.1 mph 08:56 6.9 mph 14.5 mph, 2016 3.7 mph, 2014
Minimum Feels-like 13.0 °C 23:52 15.6 °C 15.8 °C, 2017 7.2 °C, 2015
Maximum Feels-like 21.5 °C 06:56 25.8 °C 24.5 °C, 2011 14.0 °C, 2020
Mean Feels-like 18.1 °C 20.6 °C 19.4 °C, 2017 11.6 °C, 2020
Air-frost Hrs 0 hrs 0 hrs 0 hrs, 2009 0 hrs, 2009
Measure Value (anomaly) Month cumul. Record High Record Low
Temperature Range 5.4 °C (-1.4) 7.9 °C (+0.2) 13.3 °C (+6.5), 2018 3.1 °C (-3.7), 2020
Humidity Range 37% 27% 61%, 2018 7%, 2020
Pressure Range 16 hPa 5 hPa 16 hPa, 2021 2 hPa, 2009
Measure Value [% of max] Month cumul. Record High Record Low
Sun Hours 0 [0%]94 hrs (77%) [30%] 10.8 [101%], 2018 0 [0%], 2020
Wet Hours 4
[Mean rain rate: 0.7 mm/h]
24 hrs (65%) [3.7%] 4, 2017 0, 2009
Cloud Cover unknown
Events None
Comments blr
Extra Comments
Issues None known
Observer Absent? No
Pond Temperature (Heath) 17.0 °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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