Daily Report for 25th July 2021

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Measure Value (anomaly) Time Month cumul. Record High Record Low
Minimum Temperature 16.7 °C (+2.0) 05:52 14.7 °C (+0.5) 19.4 °C (+4.7), 2019 10.4 °C (-4.3), 2011
Maximum Temperature 21.2 °C (-2.1) 13:50 23.8 °C (+0.8) 36.8 °C (+13.5), 2019 20.2 °C (-3.1), 2023
Mean Temperature 17.9 °C (-0.1) 19.1 °C (+0.7) 28.4 °C, 2019 15.5 °C, 2015
Minimum Humidity 79% 13:59 61% 83%, 2024 32%, 2012
Maximum Humidity 95% 22:48 91% 95%, 2009 70%, 2011
Mean Humidity 90% 78% 90%, 2021 50%, 2012
Minimum Pressure 1008 hPa 04:47 1015 hPa 1019 hPa, 2025 1004 hPa, 2015
Maximum Pressure 1011 hPa 22:54 1020 hPa 1023 hPa, 2009 1011 hPa, 2021
Mean Pressure 1009 hPa 1017 hPa 1020 hPa, 2025 1009 hPa, 2020
Mean Wind Speed 2.4 mph (-1.9) 2.7 mph (-1.6) 6.8 mph, 2022 2.3 mph, 2018
Maximum Wind Speed 8.1 mph 13:49 10.4 mph 18.7 mph, 2020 8.1 mph, 2021
Maximum Gust 14.8 mph 15:30 15.5 mph 27.4 mph, 2016 10.7 mph, 2011
Mean Wind Direction NNE
Rainfall 38.4 mm 105.1 mm (283%) 38.4 mm, 2021
Maximum Hourly Rain 25.5 mm 17:17 25.5 mm, 2021
Maximum 10-min Rain 10.4 mm 16:43 10.4 mm, 2021
Maximum Rain Rate 102 mm/h 16:43 102 mm/h, 2014
Minimum Dew Point 15.1 °C 03:04 12.5 °C 15.1 °C, 2021 4.3 °C, 2011
Maximum Dew Point 17.8 °C 13:46 17.1 °C 21.1 °C, 2019 11.0 °C, 2011
Mean Dew Point 16.2 °C 14.8 °C 17.4 °C, 2019 7.5 °C, 2011
Measure Value Time Month cumul. Record High Record Low
Night Minimum (21-09) 16.7 °C 06:00 14.8 °C 19.4 °C, 2019 10.4 °C, 2011
Day Maximum (09-21) 21.2 °C 13:51 23.8 °C 36.8 °C, 2019 20.2 °C, 2023
Max 10m Temp Rise 0.4 °C 11:04 0.6 °C 1.1 °C, 2012 0.3 °C, 2024
Max 1hr Temp Rise 1.4 °C 11:14 2.2 °C 4.7 °C, 2012 1.3 °C, 2024
Max 1hr Hum Rise 10% 14:56 10% 28%, 2014 4%, 2025
Max 10m Temp Fall 0.8 °C 16:47 0.6 °C 2.6 °C, 2014 0.4 °C, 2010
Max 1hr Temp Fall 1.9 °C 14:49 2.2 °C 5.6 °C, 2014 1.2 °C, 2010
Max 1hr Hum Fall 5% 11:22 9% 20%, 2015 5%, 2021
Max 10m Wind Speed 6.1 mph 15:33 7.4 mph 12.7 mph, 2016 3.5 mph, 2009
Minimum Feels-like 20.8 °C 04:59 17.5 °C 23.1 °C, 2019 10.4 °C, 2011
Maximum Feels-like 27.1 °C 13:46 28.9 °C 44.6 °C, 2019 21.8 °C, 2023
Mean Feels-like 22.6 °C 23.0 °C 34.1 °C, 2019 16.1 °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 4.5 °C (-4.1) 9.1 °C (+0.3) 17.4 °C (+8.8), 2019 4.4 °C (-4.2), 2024
Humidity Range 16% 31% 52%, 2009 12%, 2024
Pressure Range 3 hPa 5 hPa 13 hPa, 2015 2 hPa, 2013
Measure Value [% of max] Month cumul. Record High Record Low
Sun Hours 0 [0%]146 hrs (92%) [40%] 13 [90%], 2012 0 [0%], 2021
Wet Hours 7
[Mean rain rate: 5 mm/h]		37 hrs (135%) [6.2%] 7, 2021 0, 2009
Cloud Cover Overcast
Events Moderate Thunderstorm
Comments Thunderstorm with Torrential rain
Extra Comments
Issues None known
Observer Absent? Yes - observations may be unreliable
Pond Temperature @ Hampstead Heath 22.0 °C
Notes
Detailed daily weather report for Hampstead nw3 in London on 25th 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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Webcam Summary of Cloud Conditions

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