Daily Report for 17th August 2009

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Measure Value (anomaly) Time Month cumul. Record High Record Low
Minimum Temperature 13.5 °C (+0.2) 06:25 14.7 °C (+1.1) 18.1 °C (+4.8), 2012 10.8 °C (-2.5), 2018
Maximum Temperature 22.4 °C (+0.1) 17:01 22.6 °C (+0.1) 27.6 °C (+5.3), 2012 20.0 °C (-2.3), 2013
Mean Temperature 17.8 °C (+0.2) 18.3 °C (+0.6) 22.2 °C, 2012 15.9 °C, 2011
Minimum Humidity 47% 17:33 56% 62%, 2020 33%, 2012
Maximum Humidity 88% 07:44 92% 98%, 2020 76%, 2012
Mean Humidity 69% 76% 85%, 2020 58%, 2012
Minimum Pressure 1015 hPa 05:27 1015 hPa 1017 hPa, 2018 1004 hPa, 2019
Maximum Pressure 1018 hPa 23:21 1018 hPa 1022 hPa, 2018 1006 hPa, 2019
Mean Pressure 1016 hPa 1017 hPa 1020 hPa, 2018 1005 hPa, 2019
Mean Wind Speed 4.1 mph (+0.1) 3.4 mph (-0.6) 7.6 mph, 2014 1.9 mph, 2015
Maximum Wind Speed 11.5 mph 9.3 mph 17.6 mph, 2014 9.0 mph, 2015
Maximum Gust 14.9 mph 17:26 13.4 mph 26.8 mph, 2013 12.1 mph, 2011
Mean Wind Direction W
Rainfall 0.0 mm 37.8 mm (138%) 6.0 mm, 2010
Maximum Hourly Rain n/a 5.5, 2010
Maximum 10-min Rain n/a 3.3, 2010
Maximum Rain Rate n/a 50, 2010
Minimum Dew Point 10.2 °C 17:33 11.2 °C 14.1 °C, 2020 4.1 °C, 2014
Maximum Dew Point 13.3 °C 09:52 16.1 °C 17.5 °C, 2012 11.3 °C, 2015
Mean Dew Point 11.7 °C 13.7 °C 15.6 °C, 2020 8.0 °C, 2015
Measure Value Time Month cumul. Record High Record Low
Night Minimum (21-09) 13.5 °C 14.7 °C 18.1 °C, 2012 10.8 °C, 2018
Day Maximum (09-21) 22.4 °C 22.6 °C 27.6 °C, 2012 20.0 °C, 2013
Max 10m Temp Rise 1.0 °C 12:38 0.5 °C 1.0 °C, 2009 0.3 °C, 2010
Max 1hr Temp Rise 1.7 °C 10:03 1.5 °C 3.1 °C, 2018 0.9 °C, 2010
Max 1hr Hum Rise 9% 23:35 7% 19%, 2020 3%, 2015
Max 10m Temp Fall 1.1 °C 22:45 0.5 °C 1.4 °C, 2014 0.3 °C, 2010
Max 1hr Temp Fall 2.1 °C 23:35 1.4 °C 3.3 °C, 2020 1.0 °C, 2010
Max 1hr Hum Fall 11% 13:29 7% 27%, 2014 4%, 2010
Max 10m Wind Speed 8.1 mph 18:19 6.4 mph 13.1 mph, 2014 5.8 mph, 2015
Minimum Feels-like 15.3 °C 06:09 16.1 °C 20.6 °C, 2012 11.8 °C, 2018
Maximum Feels-like 24.3 °C 16:57 25.0 °C 29.9 °C, 2012 20.6 °C, 2015
Mean Feels-like 19.9 °C 20.4 °C 25.0 °C, 2012 17.2 °C, 2015
Air-frost Hrs 0 hrs 0 hrs 0 hrs, 2009 0 hrs, 2009
Measure Value (anomaly) Month cumul. Record High Record Low
Temperature Range 8.9 °C (-0.1) 8.0 °C (-1.0) 12.0 °C (+3.0), 2016 5.2 °C (-3.8), 2010
Humidity Range 41% 36% 49%, 2016 32%, 2010
Pressure Range 3 hPa 3 hPa 10 hPa, 2013 2 hPa, 2011
Measure Value [% of max] Month cumul. Record High Record Low
Sun Hours 5 [38%]76 hrs (72%) [33%] 12 [91%], 2016 1 [8%], 2011
Wet Hours 014 hrs (66%) [3.4%] 2.5, 2017 0, 2009
Cloud Cover not available
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.
View monthly summary

Daily Graph of Conditions

daygraph daygraph 2 daygraph-wdir

Webcam Summary of Cloud Conditions


Webcam summary not available for this day

Wind rose