Daily Report for 11th May 2009

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Measure Value (anomaly) Time Month cumul. Record High Record Low
Minimum Temperature 6.9 °C (-0.5) 05:47 7.9 °C (+1.0) 14.7 °C (+7.2), 2016 3.1 °C (-4.3), 2010
Maximum Temperature 17.0 °C (+1.1) 15:36 17.6 °C (+2.2) 21.7 °C (+5.8), 2015 9.2 °C (-6.7), 2010
Mean Temperature 11.2 °C (+0.3) 12.4 °C (+1.6) 16.8 °C, 2015 6.8 °C, 2010
Minimum Humidity 38% 16:11 44% 80%, 2016 37%, 2012
Maximum Humidity 81% 07:35 83% 94%, 2016 72%, 2020
Mean Humidity 60% 65% 88%, 2016 60%, 2020
Minimum Pressure 1021 hPa 11:07 1018 hPa 1021 hPa, 2009 993 hPa, 2017
Maximum Pressure 1023 hPa 17:24 1022 hPa 1033 hPa, 2012 1001 hPa, 2017
Mean Pressure 1022 hPa 1020 hPa 1023 hPa, 2012 995 hPa, 2017
Mean Wind Speed n/a (-4.7) 0.0 mph (-4.7) 9.9, 2014 2, 2019
Maximum Wind Speed n/a 0.0 mph 18.5, 2013 8.6, 2016
Maximum Gust n/a 0.0 mph 30, 2020 11.5, 2016
Mean Wind Direction n/a
Rainfall 0.0 mm 1.3 mm (7%) 17.7 mm, 2016
Maximum Hourly Rain n/a 8.1, 2016
Maximum 10-min Rain n/a 4.1, 2016
Maximum Rain Rate n/a 54, 2016
Minimum Dew Point 0.7 °C 22:11 2.4 °C 8.3 °C, 2016 -1.5 °C, 2020
Maximum Dew Point 6.2 °C 10:30 8.4 °C 18.8 °C, 2016 1.4 °C, 2010
Mean Dew Point 3.3 °C 5.5 °C 14.4 °C, 2016 -0.2 °C, 2010
Measure Value Time Month cumul. Record High Record Low
Night Minimum (21-09) 6.9 °C 8.1 °C 14.7 °C, 2016 3.1 °C, 2010
Day Maximum (09-21) 17.0 °C 17.6 °C 21.7 °C, 2015 9.2 °C, 2010
Max 10m Temp Rise 0.6 °C 10:06 0.8 °C 1.0 °C, 2011 0.4 °C, 2010
Max 1hr Temp Rise 1.9 °C 10:57 2.5 °C 4.4 °C, 2018 1.2 °C, 2016
Max 1hr Hum Rise 6% 20:11 8% 24%, 2013 3%, 2016
Max 10m Temp Fall 0.5 °C 17:34 0.5 °C 1.3 °C, 2013 0.3 °C, 2010
Max 1hr Temp Fall 2.1 °C 19:31 1.7 °C 4.0 °C, 2013 1.2 °C, 2010
Max 1hr Hum Fall 13% 12:34 14% 20%, 2018 9%, 2015
Max 10m Wind Speed n/a 0.0 mph 13.8, 2020 5.5, 2010
Minimum Feels-like n/a 0.0 °C 14.9, 2016 -0.7, 2020
Maximum Feels-like n/a 0.0 °C 24.6, 2016 7.9, 2010
Mean Feels-like n/a 0.0 °C 20.2, 2016 4.9, 2010
Air-frost Hrs 0 hrs 0 hrs 0 hrs, 2009 0 hrs, 2009
Measure Value (anomaly) Month cumul. Record High Record Low
Temperature Range 10.1 °C (+1.6) 9.7 °C (+1.2) 14.5 °C (+6.0), 2017 4.9 °C (-3.6), 2016
Humidity Range 43% 40% 53%, 2012 14%, 2016
Pressure Range 2 hPa 4 hPa 20 hPa, 2019 2 hPa, 2009
Measure Value [% of max] Month cumul. Record High Record Low
Sun Hours 11.6 [83%]72 hrs (118%) [48%] 11.6 [83%], 2009 0.5 [4%], 2016
Wet Hours 02.8 hrs (20%) [1.1%] 8, 2016 0, 2009
Cloud Cover not available
Events None
Comments -
Extra Comments
Issues Tmax corrected as unreliable
Observer Absent? No
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

daygraph daygraph 2 daygraph-wdir

Webcam Summary of Cloud Conditions


Webcam summary not available for this day

Wind rose