Daily Report for 21st April 2012

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Measure Value (anomaly) Time Month cumul. Record High Record Low
Minimum Temperature 3.7 °C (-2.6) 06:12 3.8 °C (-2.0) 11.6 °C (+5.3), 2011 0.2 °C (-6.1), 2013
Maximum Temperature 14.2 °C (-0.7) 16:30 12.3 °C (-1.8) 24.4 °C (+9.5), 2011 11.1 °C (-3.8), 2024
Mean Temperature 8.5 °C (-1.6) 8.0 °C (-1.9) 17.5 °C, 2011 7.6 °C, 2024
Minimum Humidity 40% 16:32 49% 68%, 2023 29%, 2019
Maximum Humidity 89% 07:14 89% 98%, 2014 66%, 2011
Mean Humidity 69% 70% 85%, 2023 48%, 2011
Minimum Pressure 994 hPa 04:03 1001 hPa 1032 hPa, 2015 994 hPa, 2012
Maximum Pressure 1002 hPa 22:43 1010 hPa 1034 hPa, 2015 1002 hPa, 2012
Mean Pressure 998 hPa 1005 hPa 1033 hPa, 2015 998 hPa, 2012
Mean Wind Speed 5.2 mph (+0.3) 4.8 mph (-0.1) 7.9 mph, 2020 1.9 mph, 2009
Maximum Wind Speed 13.0 mph 13.5 mph 18.0 mph, 2020 9.4 mph, 2010
Maximum Gust 22.1 mph 20:54 19.3 mph 30.0 mph, 2020 12.7 mph, 2018
Mean Wind Direction W
Rainfall 0.9 mm 45.4 mm (154%) 4.4 mm, 2014
Maximum Hourly Rain 0.9 mm 21:12 2.2 mm, 2014
Maximum 10-min Rain 0.6 mm 21:12 0.9 mm, 2014
Maximum Rain Rate 2.7 mm/h 21:13 11 mm/h, 2014
Minimum Dew Point 0.2 °C 14:24 -0.7 °C 8.7 °C, 2018 -3.7 °C, 2010
Maximum Dew Point 4.6 °C 08:11 5.8 °C 14.1 °C, 2018 0.7 °C, 2010
Mean Dew Point 2.8 °C 2.6 °C 11.2 °C, 2018 -1.6 °C, 2010
Measure Value Time Month cumul. Record High Record Low
Night Minimum (21-09) 3.7 °C 06:11 4.1 °C 11.6 °C, 2011 0.2 °C, 2013
Day Maximum (09-21) 14.2 °C 16:30 12.3 °C 24.4 °C, 2011 11.1 °C, 2024
Max 10m Temp Rise 0.9 °C 07:50 0.8 °C 1.4 °C, 2013 0.4 °C, 2017
Max 1hr Temp Rise 2.8 °C 08:29 2.7 °C 5.7 °C, 2013 1.3 °C, 2017
Max 1hr Hum Rise 12% 19:28 12% 20%, 2014 4%, 2017
Max 10m Temp Fall 0.9 °C 18:58 0.8 °C 0.9 °C, 2012 0.3 °C, 2019
Max 1hr Temp Fall 2.4 °C 19:22 2.2 °C 2.9 °C, 2014 1.5 °C, 2017
Max 1hr Hum Fall 12% 10:39 14% 25%, 2014 8%, 2010
Max 10m Wind Speed 10.1 mph 17:02 9.2 mph 13.3 mph, 2020 6.9 mph, 2018
Minimum Feels-like 1.0 °C 06:22 1.3 °C 11.7 °C, 2018 -0.9 °C, 2013
Maximum Feels-like 14.2 °C 16:29 12.2 °C 26.2 °C, 2018 11.1 °C, 2024
Mean Feels-like 7.4 °C 7.0 °C 18.8 °C, 2018 5.5 °C, 2024
Air-frost Hrs 0 hrs 0.2 hrs 0 hrs, 2009 0 hrs, 2009
Measure Value (anomaly) Month cumul. Record High Record Low
Temperature Range 10.5 °C (+1.9) 8.4 °C (+0.2) 16.2 °C (+7.6), 2019 5.4 °C (-3.2), 2023
Humidity Range 49% 40% 58%, 2014 24%, 2023
Pressure Range 8 hPa 9 hPa 14 hPa, 2019 2 hPa, 2010
Measure Value [% of max] Month cumul. Record High Record Low
Sun Hours 5 [39%]89 hrs (80%) [34%] 13 [101%], 2019 0 [0%], 2017
Wet Hours 1
[Mean rain rate: 0.9 mm/h]		49 hrs (153%) [9.8%] 4, 2014 0, 2009
Cloud Cover Partly Cloudy with periods of Mostly Sunny
Events Hail: small stones
Comments 12 Slight Hail ; 19, 21 Light Showers
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 21st April 2012.
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

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Webcam Summary of Cloud Conditions

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Wind rose