Daily Report for 12th July 2021

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Measure Value (anomaly) Time Month cumul. Record High Record Low
Minimum Temperature 13.9 °C (-0.2) 06:07 14.0 °C (+0.3) 17.2 °C (+3.1), 2019 8.9 °C (-5.2), 2020
Maximum Temperature 21.8 °C (-1.3) 14:41 21.3 °C (-1.4) 26.7 °C (+3.6), 2014 18.8 °C (-4.3), 2011
Mean Temperature 16.5 °C (-0.7) 17.4 °C (-0.6) 20.6 °C, 2019 14.5 °C, 2012
Minimum Humidity 69% 14:38 64% 69%, 2021 35%, 2020
Maximum Humidity 94% 22:53 92% 97%, 2009 74%, 2010
Mean Humidity 88% 79% 88%, 2021 59%, 2010
Minimum Pressure 1011 hPa 15:37 1011 hPa 1027 hPa, 2020 1005 hPa, 2012
Maximum Pressure 1015 hPa 00:00 1017 hPa 1030 hPa, 2020 1010 hPa, 2009
Mean Pressure 1012 hPa 1014 hPa 1029 hPa, 2020 1008 hPa, 2009
Mean Wind Speed 1.1 mph (-3.2) 3.1 mph (-1.2) 6.4 mph, 2015 1.1 mph, 2021
Maximum Wind Speed 7.6 mph 10:22 10.8 mph 14.5 mph, 2016 6.9 mph, 2013
Maximum Gust 11.4 mph 10:22 15.5 mph 21.0 mph, 2016 10.9 mph, 2013
Mean Wind Direction NE
Rainfall 42.0 mm 60.0 mm (337%) 42.0 mm, 2021
Maximum Hourly Rain 20.0 mm 17:38 20.0 mm, 2021
Maximum 10-min Rain 6.0 mm 16:00 6.0 mm, 2016
Maximum Rain Rate 100 mm/h 15:55 126 mm/h, 2016
Minimum Dew Point 12.6 °C 07:56 11.7 °C 12.6 °C, 2021 6.5 °C, 2012
Maximum Dew Point 16.8 °C 14:26 15.5 °C 17.2 °C, 2014 11.7 °C, 2020
Mean Dew Point 14.5 °C 13.7 °C 14.5 °C, 2021 9.3 °C, 2020
Measure Value Time Month cumul. Record High Record Low
Night Minimum (21-09) 13.9 °C 06:06 14.1 °C 17.3 °C, 2010 8.9 °C, 2020
Day Maximum (09-21) 21.8 °C 14:42 21.3 °C 26.7 °C, 2014 18.8 °C, 2011
Max 10m Temp Rise 0.7 °C 12:04 0.6 °C 1.0 °C, 2014 0.4 °C, 2011
Max 1hr Temp Rise 2.4 °C 12:38 2.2 °C 3.7 °C, 2020 1.7 °C, 2016
Max 1hr Hum Rise 15% 16:40 10% 21%, 2012 7%, 2019
Max 10m Temp Fall 0.8 °C 16:29 0.6 °C 0.9 °C, 2016 0.4 °C, 2010
Max 1hr Temp Fall 3.3 °C 16:56 2.0 °C 3.3 °C, 2020 1.6 °C, 2019
Max 1hr Hum Fall 11% 12:42 10% 15%, 2014 7%, 2016
Max 10m Wind Speed 5.0 mph 10:27 7.8 mph 11.8 mph, 2012 5.0 mph, 2021
Minimum Feels-like 16.6 °C 06:52 16.4 °C 20.5 °C, 2019 9.0 °C, 2020
Maximum Feels-like 26.7 °C 14:26 25.3 °C 29.7 °C, 2014 19.7 °C, 2012
Mean Feels-like 20.2 °C 20.6 °C 23.9 °C, 2019 15.7 °C, 2012
Air-frost Hrs 0 hrs 0 hrs 0 hrs, 2009 0 hrs, 2009
Measure Value (anomaly) Month cumul. Record High Record Low
Temperature Range 7.9 °C (-1.1) 7.3 °C (-1.7) 15.7 °C (+6.7), 2020 4.5 °C (-4.5), 2011
Humidity Range 25% 28% 59%, 2020 21%, 2011
Pressure Range 4 hPa 6 hPa 17 hPa, 2017 2 hPa, 2015
Measure Value [% of max] Month cumul. Record High Record Low
Sun Hours 1 [7%]33 hrs (43%) [18%] 13 [87%], 2020 0.1 [1%], 2015
Wet Hours 8
[Mean rain rate: 5 mm/h]
26 hrs (198%) [9%] 8, 2012 0, 2011
Cloud Cover am: Mostly Cloudy
pm: Overcast
Events Thunder
Comments Torrential rn with thunder
Extra Comments some areas to the west, notable south hamps, recorded flooding with over 100mm rain
Issues rain gauge blocked causing slow tips and much of the rain delayed to following days. rain largely accurate but rates estimated
Observer Absent? Yes - observations may be unreliable
Pond Temperature (Heath) 20.5 °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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Wind rose