Daily Report for 18th November 2020

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Measure Value (anomaly) Time Month cumul. Record High Record Low
Minimum Temperature 8.2 °C (+3.5) 23:46 7.7 °C (+2.0) 10.9 °C (+6.2), 2009 -0.1 °C (-4.8), 2019
Maximum Temperature 15.2 °C (+5.4) 12:16 13.4 °C (+2.9) 15.2 °C (+5.4), 2020 7.3 °C (-2.5), 2016
Mean Temperature 12.1 °C (+4.5) 10.7 °C (+2.5) 12.7 °C, 2015 4.7 °C, 2012
Minimum Humidity 70% 12:14 76% 92%, 2013 60%, 2016
Maximum Humidity 92% 16:55 94% 98%, 2010 77%, 2016
Mean Humidity 82% 87% 96%, 2013 70%, 2016
Minimum Pressure 1012 hPa 16:07 1013 hPa 1028 hPa, 2021 991 hPa, 2016
Maximum Pressure 1022 hPa 00:00 1023 hPa 1031 hPa, 2021 998 hPa, 2016
Mean Pressure 1017 hPa 1018 hPa 1030 hPa, 2021 994 hPa, 2016
Mean Wind Speed 9.4 mph (+4.8) 4.9 mph (+0.3) 11.0 mph, 2009 1.6 mph, 2012
Maximum Wind Speed 17.3 mph 13:30 12.3 mph 22.8 mph, 2015 5.4 mph, 2012
Maximum Gust 30.8 mph 16:42 20.5 mph 37.1 mph, 2015 7.6 mph, 2012
Mean Wind Direction SW
Rainfall 0.2 mm 29.7 mm (83%) 3.0 mm, 2010
Maximum Hourly Rain 0.2 mm 0.9 mm, 2017
Maximum 10-min Rain 0.2 mm 0.5 mm, 2010
Maximum Rain Rate n/a 8, 2010
Minimum Dew Point 4.6 °C 23:46 5.7 °C 7.2 °C, 2009 -1.4 °C, 2019
Maximum Dew Point 13.1 °C 16:55 11.1 °C 13.1 °C, 2020 2.6 °C, 2016
Mean Dew Point 9.1 °C 8.5 °C 9.1 °C, 2020 0.3 °C, 2016
Measure Value Time Month cumul. Record High Record Low
Night Minimum (21-09) * 11.6 °C * 08:06 8.7 °C 11.6 °C, 2020 1.0 °C, 2012
Day Maximum (09-21) 15.2 °C 12:20 13.3 °C 15.2 °C, 2020 7.2 °C, 2016
Max 10m Temp Rise 0.4 °C 09:09 0.4 °C 0.6 °C, 2012 0.1 °C, 2013
Max 1hr Temp Rise 1.3 °C 10:50 1.4 °C 1.9 °C, 2012 0.3 °C, 2013
Max 1hr Hum Rise 11% 13:27 6% 11%, 2020 2%, 2013
Max 10m Temp Fall 1.0 °C 17:04 0.5 °C 1.0 °C, 2020 0.2 °C, 2010
Max 1hr Temp Fall 3.0 °C 17:51 1.4 °C 3.0 °C, 2020 0.5 °C, 2009
Max 1hr Hum Fall 11% 19:11 7% 13%, 2018 3%, 2021
Max 10m Wind Speed 14.0 mph 13:10 7.5 mph 16.9 mph, 2015 4.1 mph, 2012
Minimum Feels-like 3.9 °C 23:41 6.6 °C 11.1 °C, 2009 -2.1 °C, 2016
Maximum Feels-like 17.3 °C 16:55 15.3 °C 17.3 °C, 2020 5.8 °C, 2016
Mean Feels-like 12.7 °C 11.5 °C 13.5 °C, 2009 1.8 °C, 2016
Air-frost Hrs 0 hrs 0 hrs 0.2 hrs, 2019 0 hrs, 2009
Measure Value (anomaly) Month cumul. Record High Record Low
Temperature Range 7.0 °C (+1.9) 5.8 °C (+0.9) 8.0 °C (+2.9), 2019 2.9 °C (-2.2), 2009
Humidity Range 22% 18% 29%, 2018 6%, 2013
Pressure Range 10 hPa 10 hPa 10 hPa, 2020 3 hPa, 2011
Measure Value [% of max] Month cumul. Record High Record Low
Sun Hours 2 [26%]50 hrs (110%) [34%] 7.8 [101%], 2018 0 [0%], 2009
Wet Hours 0.537 hrs (97%) [8.4%] 4, 2010 0, 2011
Cloud Cover am: Partly Cloudy
pm: Overcast
Events None
Comments pm shs
Extra Comments rainbow 1240
Issues wind from harpenden
Observer Absent? Yes - observations may be unreliable
Pond Temperature (Heath) 10.5 °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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