Daily Report for 31st December 2018

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Measure Value (anomaly) Time Month cumul. Record High Record Low
Minimum Temperature 8.6 °C (+5.9) 08:01 5.3 °C (+2.1) 10.6 °C (+7.9), 2011 -1.8 °C (-4.5), 2020
Maximum Temperature 9.8 °C (+2.7) 00:35 9.9 °C (+2.1) 12.9 °C (+5.8), 2017 0.8 °C (-6.3), 2020
Mean Temperature 9.2 °C (+4.3) 7.8 °C (+2.1) 11.7 °C, 2011 -0.3 °C, 2020
Minimum Humidity 80% 14:52 79% 89%, 2020 62%, 2015
Maximum Humidity 90% 08:09 93% 98%, 2009 83%, 2016
Mean Humidity 84% 87% 95%, 2010 74%, 2015
Minimum Pressure 1035 hPa 23:59 1013 hPa 1035 hPa, 2018 992 hPa, 2017
Maximum Pressure 1038 hPa 09:46 1022 hPa 1038 hPa, 2018 999 hPa, 2017
Mean Pressure 1036 hPa 1017 hPa 1036 hPa, 2018 994 hPa, 2017
Mean Wind Speed 3.2 mph (-1.9) 4.9 mph (-0.2) 10.1 mph, 2017 1.5 mph, 2010
Maximum Wind Speed 9.4 mph 16:10 13.4 mph 22.0 mph, 2017 6.4 mph, 2010
Maximum Gust 15.0 mph 16:38 21.3 mph 34.6 mph, 2017 8.1 mph, 2010
Mean Wind Direction WNW
Rainfall 0.0 mm 61.5 mm (112%) 6.4 mm, 2017
Maximum Hourly Rain n/a 5.1, 2017
Maximum 10-min Rain n/a 3.3, 2017
Maximum Rain Rate n/a 42, 2015
Minimum Dew Point 5.3 °C 23:37 3.3 °C 9.8 °C, 2011 -2.9 °C, 2020
Maximum Dew Point 7.7 °C 00:10 8.0 °C 11.4 °C, 2017 -0.3 °C, 2020
Mean Dew Point 6.6 °C 5.8 °C 10.3 °C, 2011 -1.4 °C, 2020
Measure Value Time Month cumul. Record High Record Low
Night Minimum (21-09) 8.6 °C 08:01 6.0 °C 10.1 °C, 2012 -1.8 °C, 2020
Day Maximum (09-21) * 9.6 °C * 14:22 9.8 °C 12.5 °C, 2011 0.8 °C, 2020
Max 10m Temp Rise 0.2 °C 13:18 0.3 °C 0.5 °C, 2019 0.1 °C, 2009
Max 1hr Temp Rise 0.4 °C 10:52 1.1 °C 1.9 °C, 2014 0.3 °C, 2009
Max 1hr Hum Rise 1% 01:22 5% 10%, 2015 1%, 2010
Max 10m Temp Fall 0.2 °C 15:36 0.4 °C 1.0 °C, 2013 0.1 °C, 2010
Max 1hr Temp Fall 0.3 °C 05:00 1.1 °C 2.3 °C, 2013 0.3 °C, 2010
Max 1hr Hum Fall 4% 09:56 6% 9%, 2015 1%, 2016
Max 10m Wind Speed 7.0 mph 23:21 10.0 mph 16.0 mph, 2017 5.0 mph, 2010
Minimum Feels-like 5.5 °C 23:13 2.5 °C 11.7 °C, 2011 -7.1 °C, 2020
Maximum Feels-like 10.1 °C 00:02 10.4 °C 14.7 °C, 2017 0.8 °C, 2020
Mean Feels-like 7.9 °C 6.7 °C 13.1 °C, 2011 -2.1 °C, 2020
Air-frost Hrs 0 hrs 0.0 hrs 13 hrs, 2020 0 hrs, 2009
Measure Value (anomaly) Month cumul. Record High Record Low
Temperature Range 1.2 °C (-3.1) 4.7 °C (-0.0) 6.6 °C (+2.3), 2014 1.2 °C (-3.1), 2018
Humidity Range 10% 15% 26%, 2015 3%, 2016
Pressure Range 3 hPa 9 hPa 16 hPa, 2012 3 hPa, 2018
Measure Value [% of max] Month cumul. Record High Record Low
Sun Hours 0 [0%]56 hrs (97%) [25%] 6 [85%], 2015 0 [0%], 2010
Wet Hours 063 hrs (102%) [8.5%] 7, 2012 0, 2010
Cloud Cover Overcast
Events None
Comments -
Extra Comments
Issues None known
Observer Absent? Yes - observations may be unreliable
Pond Temperature (Heath) 0.0 °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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Daily Graph of Conditions

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Webcam Summary of Cloud Conditions

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Wind rose