Daily Report for 15th January 2021

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Measure Value (anomaly) Time Month cumul. Record High Record Low
Minimum Temperature -0.9 °C (-3.3) 21:06 0.2 °C (-2.2) 7.8 °C (+5.4), 2011 -2.6 °C (-5.0), 2013
Maximum Temperature 3.2 °C (-3.8) 15:29 5.2 °C (-1.8) 12.3 °C (+5.3), 2020 1.6 °C (-5.4), 2013
Mean Temperature 1.1 °C (-3.5) 2.7 °C (-2.0) 10.3 °C, 2011 0.6 °C, 2013
Minimum Humidity 86% 23:50 85% 98%, 2010 53%, 2015
Maximum Humidity 96% 22:25 94% 98%, 2010 83%, 2016
Mean Humidity 92% 91% 98%, 2010 74%, 2015
Minimum Pressure 1026 hPa 00:00 1017 hPa 1026 hPa, 2021 987 hPa, 2015
Maximum Pressure 1033 hPa 11:14 1023 hPa 1033 hPa, 2021 996 hPa, 2015
Mean Pressure 1030 hPa 1020 hPa 1030 hPa, 2021 990 hPa, 2015
Mean Wind Speed 0.7 mph (-4.5) 3.4 mph (-1.8) 10.8 mph, 2015 0.7 mph, 2021
Maximum Wind Speed 7.8 mph 00:36 10.4 mph 28.6 mph, 2020 7.8 mph, 2021
Maximum Gust 12.5 mph 00:39 16.7 mph 42.6 mph, 2020 12.5 mph, 2021
Mean Wind Direction N
Rainfall 0.0 mm 37.0 mm (139%) 9.1 mm, 2020
Maximum Hourly Rain n/a 3.1, 2020
Maximum 10-min Rain n/a 2, 2018
Maximum Rain Rate n/a 66, 2018
Minimum Dew Point -1.9 °C 21:02 -1.0 °C 5.6 °C, 2011 -4.2 °C, 2013
Maximum Dew Point 1.6 °C 15:53 3.6 °C 10.3 °C, 2020 -0.5 °C, 2016
Mean Dew Point -0.1 °C 1.4 °C 8.6 °C, 2014 -1.7 °C, 2016
Measure Value Time Month cumul. Record High Record Low
Night Minimum (21-09) * -0.1 °C * 04:26 1.3 °C 7.8 °C, 2011 -0.1 °C, 2012
Day Maximum (09-21) 3.2 °C 15:09 4.8 °C 11.2 °C, 2011 1.6 °C, 2013
Max 10m Temp Rise 0.5 °C 22:25 0.3 °C 0.5 °C, 2012 0.2 °C, 2011
Max 1hr Temp Rise 1.9 °C 22:55 0.9 °C 1.9 °C, 2021 0.5 °C, 2015
Max 1hr Hum Rise 3% 18:41 4% 8%, 2016 0%, 2010
Max 10m Temp Fall 0.4 °C 18:35 0.4 °C 1.2 °C, 2020 0.2 °C, 2010
Max 1hr Temp Fall 1.6 °C 18:33 1.2 °C 3.1 °C, 2020 0.4 °C, 2011
Max 1hr Hum Fall 8% 23:25 4% 18%, 2012 0%, 2010
Max 10m Wind Speed 5.0 mph 00:11 8.3 mph 20.3 mph, 2020 5.0 mph, 2021
Minimum Feels-like -4.0 °C 00:39 -4.0 °C 4.3 °C, 2011 -4.6 °C, 2013
Maximum Feels-like 3.2 °C 14:14 4.8 °C 13.7 °C, 2020 1.5 °C, 2013
Mean Feels-like 0.4 °C 0.7 °C 9.9 °C, 2011 -1.8 °C, 2013
Air-frost Hrs 3 hrs 4 hrs 5 hrs, 2013 0 hrs, 2010
Measure Value (anomaly) Month cumul. Record High Record Low
Temperature Range 4.1 °C (-0.5) 5.0 °C (+0.4) 8.8 °C (+4.2), 2017 2.0 °C (-2.6), 2009
Humidity Range 10% 10% 40%, 2015 0%, 2010
Pressure Range 7 hPa 6 hPa 22 hPa, 2020 2 hPa, 2009
Measure Value [% of max] Month cumul. Record High Record Low
Sun Hours 0.3 [4%]18 hrs (63%) [16%] 7.1 [95%], 2012 0 [0%], 2010
Wet Hours 040 hrs (123%) [11%] 13, 2017 , 2009
Cloud Cover Mostly Cloudy with periods of Overcast
Events Air Frost
Comments -
Extra Comments
Issues None known
Observer Absent? Yes - observations may be unreliable
Pond Temperature (Heath) 4.5 °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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