Daily Report for 20th May 2009

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Measure Value (anomaly) Time Month cumul. Record High Record Low
Minimum Temperature 8.3 °C (-1.2) 05:34 8.3 °C (-0.1) 14.1 °C (+4.6), 2014 5.1 °C (-4.4), 2015
Maximum Temperature 19.2 °C (+1.0) 17:24 17.1 °C (-0.1) 27.4 °C (+9.2), 2020 11.7 °C (-6.5), 2012
Mean Temperature 13.5 °C (-0.1) 12.4 °C (-0.1) 21.1 °C, 2020 10.1 °C, 2012
Minimum Humidity 44% 17:37 48% 80%, 2012 36%, 2020
Maximum Humidity 92% 06:50 86% 93%, 2013 67%, 2011
Mean Humidity 68% 69% 85%, 2013 53%, 2011
Minimum Pressure 1017 hPa 20:31 1014 hPa 1030 hPa, 2010 1002 hPa, 2021
Maximum Pressure 1021 hPa 09:35 1019 hPa 1033 hPa, 2010 1010 hPa, 2014
Mean Pressure 1019 hPa 1017 hPa 1032 hPa, 2010 1006 hPa, 2014
Mean Wind Speed 4.9 mph (+0.2) 6.4 mph (+1.7) 8.1 mph, 2021 1.5 mph, 2019
Maximum Wind Speed n/a 0.0 mph 22.2, 2021 7.1, 2010
Maximum Gust 21.0 mph 25.1 mph 35.4 mph, 2021 10.0 mph, 2010
Mean Wind Direction n/a
Rainfall 0.0 mm 12.4 mm (42%) 4.1 mm, 2022
Maximum Hourly Rain n/a 1.9, 2022
Maximum 10-min Rain n/a 0.8, 2017
Maximum Rain Rate n/a 18, 2017
Minimum Dew Point 5.2 °C 20:29 3.6 °C 8.3 °C, 2010 1.1 °C, 2015
Maximum Dew Point 9.5 °C 08:51 9.2 °C 14.9 °C, 2010 5.7 °C, 2015
Mean Dew Point 7.2 °C 6.5 °C 11.6 °C, 2010 3.2 °C, 2015
Measure Value Time Month cumul. Record High Record Low
Night Minimum (21-09) 8.3 °C 8.6 °C 15.3 °C, 2014 5.1 °C, 2015
Day Maximum (09-21) 19.2 °C 17.1 °C 27.4 °C, 2020 11.7 °C, 2012
Max 10m Temp Rise 0.9 °C 12:38 0.8 °C 0.9 °C, 2009 0.4 °C, 2012
Max 1hr Temp Rise 2.4 °C 12:42 2.2 °C 3.6 °C, 2023 1.1 °C, 2012
Max 1hr Hum Rise 8% 22:45 9% 16%, 2021 2%, 2012
Max 10m Temp Fall 0.3 °C 13:27 0.5 °C 0.9 °C, 2017 0.2 °C, 2012
Max 1hr Temp Fall 1.5 °C 19:18 1.5 °C 2.8 °C, 2019 0.5 °C, 2012
Max 1hr Hum Fall 10% 11:16 14% 15%, 2018 5%, 2012
Max 10m Wind Speed n/a 0.0 mph 19, 2021 4.9, 2019
Minimum Feels-like n/a 0.0 °C 14.9, 2016 2, 2015
Maximum Feels-like n/a 0.0 °C 30.5, 2020 12.4, 2012
Mean Feels-like n/a 0.0 °C 23.1, 2020 9.5, 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 10.9 °C (+2.2) 8.8 °C (-0.0) 15.1 °C (+6.4), 2020 3.1 °C (-5.6), 2012
Humidity Range 48% 38% 50%, 2020 7%, 2012
Pressure Range 4 hPa 5 hPa 20 hPa, 2021 2 hPa, 2012
Measure Value [% of max] Month cumul. Record High Record Low
Sun Hours 5.8 [40%]106 hrs (88%) [38%] 14.4 [100%], 2018 0 [0%], 2012
Wet Hours 013 hrs (52%) [2.8%] 4, 2022 0, 2009
Cloud Cover not available
Events None
Comments -
Extra Comments
Issues None known
Observer Absent? No
Pond Temperature (Heath) 0.0 °C
Notes
Detailed daily weather report for Hampstead nw3 in London on 20th May 2009.
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 derived based on analysis of webcam observations, but may use data from our closest site, Heathrow, when needed.
Wet hrs are dervied algorithmically from rainfall data, though may be adjusted manually.
Rainfall totals may be manually adjusted after the fact to correct delayed or erroneous data.
Cloud cover and Events are manually reported, often with multi-week delays.
Data is generally reliable and accurate but should always be viewed with some quantity of salt to hand.
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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