Daily Report for 26th September 2020

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Measure Value (anomaly) Time Month cumul. Record High Record Low
Minimum Temperature 6.5 °C (-3.9) 12:32 11.3 °C (+0.1) 15.0 °C (+4.6), 2011 6.5 °C (-3.9), 2020
Maximum Temperature 11.6 °C (-5.5) 22:00 21.0 °C (+2.1) 23.8 °C (+6.7), 2018 11.6 °C (-5.5), 2020
Mean Temperature 9.0 °C (-4.7) 16.0 °C (+1.1) 17.7 °C, 2011 9.0 °C, 2020
Minimum Humidity 65% 01:06 55% 75%, 2012 33%, 2018
Maximum Humidity 90% 18:52 90% 94%, 2019 84%, 2016
Mean Humidity 77% 75% 85%, 2012 64%, 2018
Minimum Pressure 1010 hPa 00:02 1016 hPa 1030 hPa, 2018 989 hPa, 2012
Maximum Pressure 1014 hPa 21:36 1021 hPa 1035 hPa, 2018 999 hPa, 2012
Mean Pressure 1012 hPa 1019 hPa 1032 hPa, 2018 992 hPa, 2012
Mean Wind Speed 5.0 mph (+1.1) 3.1 mph (-0.8) 6.5 mph, 2019 1.1 mph, 2009
Maximum Wind Speed 12.2 mph 05:54 11.7 mph 15.3 mph, 2016 4.5 mph, 2009
Maximum Gust 26.5 mph 18:22 19.9 mph 26.5 mph, 2020 6.4 mph, 2009
Mean Wind Direction NW
Rainfall 0.5 mm 14.3 mm (34%) 4.1 mm, 2012
Maximum Hourly Rain 0.2 mm 3.0 mm, 2011
Maximum 10-min Rain n/a 2.5, 2016
Maximum Rain Rate n/a 66, 2016
Minimum Dew Point 2.0 °C 12:32 8.8 °C 13.3 °C, 2011 2.0 °C, 2020
Maximum Dew Point 7.8 °C 19:11 13.7 °C 16.7 °C, 2011 7.8 °C, 2020
Mean Dew Point 5.1 °C 11.4 °C 14.5 °C, 2011 5.1 °C, 2020
Measure Value Time Month cumul. Record High Record Low
Night Minimum (21-09) 6.5 °C 07:47 11.7 °C 16.3 °C, 2011 6.5 °C, 2020
Day Maximum (09-21) 11.6 °C 20:56 21.0 °C 23.8 °C, 2018 11.6 °C, 2020
Max 10m Temp Rise 0.3 °C 18:22 0.6 °C 0.9 °C, 2018 0.3 °C, 2020
Max 1hr Temp Rise 1.0 °C 19:17 2.4 °C 3.5 °C, 2018 1.0 °C, 2020
Max 1hr Hum Rise 4% 18:33 10% 15%, 2016 4%, 2020
Max 10m Temp Fall 0.2 °C 01:05 0.6 °C 1.3 °C, 2016 0.2 °C, 2020
Max 1hr Temp Fall 0.7 °C 02:33 2.1 °C 4.0 °C, 2018 0.7 °C, 2020
Max 1hr Hum Fall 4% 21:01 11% 15%, 2018 3%, 2010
Max 10m Wind Speed 8.0 mph 21:30 8.0 mph 12.1 mph, 2016 2.9 mph, 2009
Minimum Feels-like 2.0 °C 06:07 11.9 °C 18.1 °C, 2011 2.0 °C, 2020
Maximum Feels-like 11.5 °C 21:12 23.8 °C 25.2 °C, 2011 11.5 °C, 2020
Mean Feels-like 8.0 °C 18.1 °C 21.4 °C, 2011 8.0 °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 5.1 °C (-1.7) 9.7 °C (+2.0) 16.1 °C (+9.3), 2018 5.1 °C (-1.7), 2012
Humidity Range 25% 35% 58%, 2018 18%, 2012
Pressure Range 4 hPa 5 hPa 10 hPa, 2011 2 hPa, 2016
Measure Value [% of max] Month cumul. Record High Record Low
Sun Hours 4 [37%]168 hrs (142%) [56%] 10.9 [101%], 2018 1 [9%], 2011
Wet Hours 0.5
[Mean rain rate: 1.0 mm/h]
13 hrs (37%) [2.1%] 6, 2012 0, 2009
Cloud Cover am: Sunny
pm: Overcast
Events None
Comments pm shs
Extra Comments
Issues 07-18 data loss. Avg and extremes reconstructed w harpenden
Observer Absent? Yes - observations may be unreliable
Pond Temperature (Heath) 14.0 °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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