Daily Report for 15th March 2021

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Measure Value (anomaly) Time Month cumul. Record High Record Low
Minimum Temperature 7.2 °C (+3.7) 11:58 3.4 °C (+0.3) 9.3 °C (+5.8), 2019 1.7 °C (-1.8), 2012
Maximum Temperature 10.2 °C (-0.0) 16:45 8.7 °C (-0.9) 17.2 °C (+7.0), 2014 6.8 °C (-3.4), 2015
Mean Temperature 8.8 °C (+1.8) 6.0 °C (-0.3) 12.1 °C, 2019 5.6 °C, 2015
Minimum Humidity 72% 11:16 66% 77%, 2011 32%, 2014
Maximum Humidity 87% 12:00 90% 98%, 2011 79%, 2014
Mean Humidity 79% 80% 91%, 2011 58%, 2014
Minimum Pressure 1015 hPa 00:00 1015 hPa 1028 hPa, 2016 988 hPa, 2018
Maximum Pressure 1028 hPa 23:57 1024 hPa 1036 hPa, 2017 993 hPa, 2018
Mean Pressure 1022 hPa 1020 hPa 1033 hPa, 2017 991 hPa, 2018
Mean Wind Speed 5.7 mph (+0.5) 5.7 mph (+0.5) 11.3 mph, 2019 1.8 mph, 2017
Maximum Wind Speed 15.9 mph 01:11 14.2 mph 24.1 mph, 2019 7.7 mph, 2017
Maximum Gust 22.8 mph 01:03 20.9 mph 47.2 mph, 2019 10.5 mph, 2017
Mean Wind Direction NNW
Rainfall 0.7 mm 15.7 mm (77%) 4.8 mm, 2018
Maximum Hourly Rain 0.7 mm 11:51 1.5 mm, 2018
Maximum 10-min Rain 0.5 mm 11:35 0.6 mm, 2013
Maximum Rain Rate 2.9 mm/h 11:35 4.4 mm/h, 2020
Minimum Dew Point 4.2 °C 23:48 0.6 °C 7.3 °C, 2019 -5.4 °C, 2013
Maximum Dew Point 6.4 °C 12:37 4.7 °C 10.2 °C, 2019 3.9 °C, 2015
Mean Dew Point 5.4 °C 2.6 °C 9.0 °C, 2019 0.7 °C, 2010
Measure Value Time Month cumul. Record High Record Low
Night Minimum (21-09) * 7.5 °C * 06:45 3.7 °C 9.3 °C, 2019 1.7 °C, 2012
Day Maximum (09-21) 10.2 °C 14:07 8.6 °C 17.2 °C, 2014 6.8 °C, 2015
Max 10m Temp Rise 0.6 °C 12:37 0.4 °C 0.9 °C, 2012 0.2 °C, 2015
Max 1hr Temp Rise 2.0 °C 13:02 1.3 °C 4.0 °C, 2012 0.6 °C, 2015
Max 1hr Hum Rise 13% 12:16 8% 13%, 2021 4%, 2011
Max 10m Temp Fall 1.2 °C 11:25 0.4 °C 1.2 °C, 2020 0.2 °C, 2015
Max 1hr Temp Fall 2.5 °C 12:03 1.3 °C 2.8 °C, 2020 0.6 °C, 2015
Max 1hr Hum Fall 11% 15:31 8% 20%, 2012 2%, 2016
Max 10m Wind Speed 12.4 mph 01:39 10.7 mph 19.3 mph, 2019 6.0 mph, 2017
Minimum Feels-like 3.5 °C 05:07 -0.2 °C 6.5 °C, 2017 -1.1 °C, 2013
Maximum Feels-like 10.2 °C 11:12 8.6 °C 17.5 °C, 2017 5.5 °C, 2015
Mean Feels-like 6.8 °C 4.1 °C 12.7 °C, 2019 2.7 °C, 2013
Air-frost Hrs 0 hrs 0.2 hrs 0 hrs, 2009 0 hrs, 2009
Measure Value (anomaly) Month cumul. Record High Record Low
Temperature Range 3.0 °C (-3.7) 5.3 °C (-1.3) 14.2 °C (+7.5), 2012 2.2 °C (-4.5), 2015
Humidity Range 15% 23% 47%, 2010 15%, 2020
Pressure Range 12 hPa 9 hPa 16 hPa, 2017 3 hPa, 2014
Measure Value [% of max] Month cumul. Record High Record Low
Sun Hours 1.1 [10%]37 hrs (74%) [24%] 10.4 [98%], 2009 0 [0%], 2013
Wet Hours 1
[Mean rain rate: 0.7 mm/h]
20 hrs (76%) [5.4%] 8, 2013 , 2009
Cloud Cover Mostly Cloudy
Events None
Comments lunch shs
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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