Daily Report for 17th July 2021

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Measure Value (anomaly) Time Month cumul. Record High Record Low
Minimum Temperature 14.8 °C (+0.4) 05:31 13.9 °C (+0.0) 18.7 °C (+4.3), 2016 12.7 °C (-1.7), 2023
Maximum Temperature 27.6 °C (+4.4) 16:27 22.2 °C (-0.7) 31.2 °C (+8.0), 2013 18.4 °C (-4.8), 2009
Mean Temperature 21.8 °C (+2.4) 17.9 °C (-0.3) 24.7 °C, 2013 15.6 °C, 2009
Minimum Humidity 52% 15:26 63% 71%, 2009 29%, 2013
Maximum Humidity 85% 05:38 91% 96%, 2009 71%, 2013
Mean Humidity 68% 78% 88%, 2009 45%, 2013
Minimum Pressure 1028 hPa 18:40 1014 hPa 1028 hPa, 2021 993 hPa, 2011
Maximum Pressure 1030 hPa 08:37 1019 hPa 1030 hPa, 2021 996 hPa, 2011
Mean Pressure 1029 hPa 1017 hPa 1029 hPa, 2021 994 hPa, 2011
Mean Wind Speed 1.9 mph (-2.4) 3.1 mph (-1.2) 8.5 mph, 2009 1.3 mph, 2024
Maximum Wind Speed 9.2 mph 10:37 10.8 mph 16.6 mph, 2016 6.3 mph, 2024
Maximum Gust 14.8 mph 10:35 15.8 mph 26.0 mph, 2009 10.4 mph, 2024
Mean Wind Direction NE
Rainfall 0.0 mm 60.0 mm (238%) 3.3 mm, 2011
Maximum Hourly Rain n/a 14:16 1.6, 2011
Maximum 10-min Rain n/a 14:16 1.1, 2011
Maximum Rain Rate n/a 50, 2011
Minimum Dew Point 12.0 °C 04:52 11.7 °C 13.6 °C, 2016 4.2 °C, 2010
Maximum Dew Point 18.3 °C 16:25 16.0 °C 19.3 °C, 2025 12.7 °C, 2010
Mean Dew Point 15.4 °C 13.9 °C 15.9 °C, 2025 9.2 °C, 2010
Measure Value Time Month cumul. Record High Record Low
Night Minimum (21-09) 14.8 °C 05:31 14.0 °C 18.7 °C, 2016 12.7 °C, 2023
Day Maximum (09-21) 27.6 °C 16:27 22.2 °C 31.2 °C, 2013 18.4 °C, 2009
Max 10m Temp Rise 0.5 °C 07:03 0.6 °C 1.6 °C, 2009 0.4 °C, 2017
Max 1hr Temp Rise 2.2 °C 08:01 2.2 °C 4.8 °C, 2022 1.7 °C, 2011
Max 1hr Hum Rise 10% 20:19 9% 19%, 2022 5%, 2010
Max 10m Temp Fall 0.5 °C 20:31 0.6 °C 1.1 °C, 2009 0.3 °C, 2012
Max 1hr Temp Fall 2.2 °C 21:14 1.9 °C 3.0 °C, 2022 1.1 °C, 2012
Max 1hr Hum Fall 8% 07:56 10% 21%, 2022 7%, 2014
Max 10m Wind Speed 7.4 mph 11:52 7.7 mph 14.2 mph, 2015 4.6 mph, 2024
Minimum Feels-like 17.2 °C 04:52 16.3 °C 23.2 °C, 2016 13.9 °C, 2011
Maximum Feels-like 33.8 °C 16:25 26.6 °C 33.8 °C, 2021 21.9 °C, 2011
Mean Feels-like 26.1 °C 21.3 °C 26.8 °C, 2016 17.6 °C, 2011
Air-frost Hrs 0 hrs 0 hrs 0 hrs, 2009 0 hrs, 2009
Measure Value (anomaly) Month cumul. Record High Record Low
Temperature Range 12.8 °C (+4.0) 8.3 °C (-0.7) 15.8 °C (+7.0), 2022 4.5 °C (-4.3), 2009
Humidity Range 33% 28% 52%, 2022 19%, 2025
Pressure Range 3 hPa 5 hPa 11 hPa, 2010 2 hPa, 2016
Measure Value [% of max] Month cumul. Record High Record Low
Sun Hours 14.7 [100%]76 hrs (69%) [30%] 14.7 [100%], 2021 1 [7%], 2025
Wet Hours 026 hrs (139%) [6.4%] 3, 2009 0, 2010
Cloud Cover Sunny
Events Maximum possible sunshine
Comments -
Extra Comments
Issues rain gauge blocked - still reporting rain from days ago
Observer Absent? Yes - observations may be unreliable
Pond Temperature @ Hampstead Heath 21.5 °C
Notes
Detailed daily weather report for Hampstead nw3 in London on 17th July 2021.
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

daycamsumFull resolution individual images at up-to 5 minute intervals

Wind rose