Daily Report for 17th December 2019

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Measure Value (anomaly) Time Month cumul. Record High Record Low
Minimum Temperature 5.8 °C (+2.7) 08:47 3.5 °C (+0.1) 11.8 °C (+8.7), 2015 -6.0 °C (-9.1), 2010
Maximum Temperature 7.4 °C (-0.3) 14:13 8.9 °C (+0.6) 15.2 °C (+7.5), 2015 -0.8 °C (-8.5), 2010
Mean Temperature 6.6 °C (+1.2) 6.3 °C (+0.4) 13.6 °C, 2015 -3.0 °C, 2010
Minimum Humidity 91% 14:11 77% 92%, 2013 67%, 2015
Maximum Humidity 95% 10:00 93% 98%, 2009 84%, 2016
Mean Humidity 93% 86% 96%, 2013 79%, 2015
Minimum Pressure 997 hPa 04:02 1001 hPa 1034 hPa, 2016 995 hPa, 2010
Maximum Pressure 1008 hPa 23:56 1014 hPa 1041 hPa, 2016 1002 hPa, 2010
Mean Pressure 1001 hPa 1008 hPa 1038 hPa, 2016 998 hPa, 2010
Mean Wind Speed 2.7 mph (-2.4) 6.1 mph (+1.0) 9.0 mph, 2009 0.7 mph, 2016
Maximum Wind Speed 8.9 mph 20:31 15.6 mph 22.8 mph, 2009 4.6 mph, 2016
Maximum Gust 12.0 mph 16:06 25.1 mph 33.1 mph, 2009 6.3 mph, 2016
Mean Wind Direction NW
Rainfall 5.3 mm 51.6 mm (171%) 6.1 mm, 2013
Maximum Hourly Rain 1.3 mm 06:41 2.1 mm, 2014
Maximum 10-min Rain 0.4 mm 04:51 0.7 mm, 2013
Maximum Rain Rate 1.9 mm/h 06:41 3.6 mm/h, 2014
Minimum Dew Point 4.5 °C 22:33 1.4 °C 8.3 °C, 2015 -8.0 °C, 2010
Maximum Dew Point 6.3 °C 00:02 6.7 °C 12.4 °C, 2015 -3.8 °C, 2010
Mean Dew Point 5.6 °C 4.2 °C 10.0 °C, 2015 -5.8 °C, 2010
Measure Value Time Month cumul. Record High Record Low
Night Minimum (21-09) 5.8 °C 08:04 4.2 °C 12.7 °C, 2015 -3.3 °C, 2010
Day Maximum (09-21) 7.4 °C 14:14 8.8 °C 15.2 °C, 2015 -0.8 °C, 2010
Max 10m Temp Rise 0.2 °C 09:33 0.3 °C 0.6 °C, 2016 0.2 °C, 2010
Max 1hr Temp Rise 0.5 °C 11:24 1.2 °C 1.7 °C, 2018 0.5 °C, 2019
Max 1hr Hum Rise 2% 17:40 5% 12%, 2009 2%, 2013
Max 10m Temp Fall 0.2 °C 22:04 0.4 °C 0.5 °C, 2010 0.1 °C, 2014
Max 1hr Temp Fall 0.7 °C 22:33 1.3 °C 1.6 °C, 2010 0.3 °C, 2014
Max 1hr Hum Fall 3% 13:27 6% 12%, 2017 2%, 2016
Max 10m Wind Speed 6.0 mph 16:45 11.7 mph 15.1 mph, 2009 3.5 mph, 2016
Minimum Feels-like 2.9 °C 01:07 -1.1 °C 13.0 °C, 2015 -9.0 °C, 2010
Maximum Feels-like 7.4 °C 14:04 8.5 °C 16.9 °C, 2015 -0.8 °C, 2010
Mean Feels-like 5.3 °C 4.2 °C 14.9 °C, 2015 -5.7 °C, 2010
Air-frost Hrs 0 hrs 0 hrs 24 hrs, 2010 0 hrs, 2011
Measure Value (anomaly) Month cumul. Record High Record Low
Temperature Range 1.6 °C (-3.0) 5.5 °C (+0.6) 9.2 °C (+4.6), 2017 1.6 °C (-3.0), 2019
Humidity Range 4% 16% 26%, 2009 4%, 2019
Pressure Range 11 hPa 13 hPa 11 hPa, 2018 4 hPa, 2009
Measure Value [% of max] Month cumul. Record High Record Low
Sun Hours 0 [0%]47 hrs (151%) [39%] 6 [86%], 2012 0 [0%], 2016
Wet Hours 12
[Mean rain rate: 0.4 mm/h]
58 hrs (171%) [14%] 12, 2019 0, 2016
Cloud Cover Overcast
Events None
Comments rn
Extra Comments
Issues None known
Observer Absent? Yes - observations may be unreliable
Pond Temperature (Heath) 5.5 °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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