Daily Report for 20th September 2018

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Measure Value (anomaly) Time Month cumul. Record High Record Low
Minimum Temperature 16.7 °C (+5.6) 07:01 12.6 °C (+0.7) 16.7 °C (+5.6), 2018 8.4 °C (-2.7), 2015
Maximum Temperature 20.6 °C (+2.4) 14:52 21.2 °C (+1.5) 23.9 °C (+5.7), 2020 17.3 °C (-0.9), 2012
Mean Temperature 18.6 °C (+4.0) 16.7 °C (+1.1) 18.6 °C, 2018 13.2 °C, 2012
Minimum Humidity 70% 16:08 53% 92%, 2014 40%, 2019
Maximum Humidity 90% 07:02 90% 96%, 2014 78%, 2012
Mean Humidity 80% 74% 94%, 2014 62%, 2012
Minimum Pressure 1000 hPa 23:59 1017 hPa 1026 hPa, 2022 994 hPa, 2023
Maximum Pressure 1014 hPa 00:01 1022 hPa 1031 hPa, 2019 1005 hPa, 2023
Mean Pressure 1010 hPa 1019 hPa 1027 hPa, 2022 1000 hPa, 2023
Mean Wind Speed 9.6 mph (+5.7) 4.9 mph (+1.0) 10.5 mph, 2023 1.2 mph, 2022
Maximum Wind Speed 23.0 mph 23:39 13.7 mph 23.2 mph, 2023 5.8 mph, 2022
Maximum Gust 34.6 mph 17:18 21.6 mph 35.7 mph, 2023 9.2 mph, 2013
Mean Wind Direction SSW
Rainfall 0.9 mm 5.3 mm (16%) 29.3 mm, 2014
Maximum Hourly Rain 0.7 mm 11:22 18.7 mm, 2014
Maximum 10-min Rain 0.2 mm 11:22 7.9 mm, 2014
Maximum Rain Rate 0.8 mm/h 11:04 126 mm/h, 2014
Minimum Dew Point 14.3 °C 00:05 9.5 °C 14.3 °C, 2018 3.0 °C, 2012
Maximum Dew Point 15.8 °C 10:56 13.9 °C 17.1 °C, 2014 8.3 °C, 2012
Mean Dew Point 15.0 °C 11.7 °C 15.6 °C, 2014 5.9 °C, 2012
Measure Value Time Month cumul. Record High Record Low
Night Minimum (21-09) 16.7 °C 07:01 12.8 °C 16.9 °C, 2023 8.2 °C, 2017
Day Maximum (09-21) 20.6 °C 14:52 21.1 °C 23.9 °C, 2020 17.3 °C, 2012
Max 10m Temp Rise 0.5 °C 14:32 0.6 °C 0.8 °C, 2022 0.3 °C, 2011
Max 1hr Temp Rise 1.5 °C 14:52 2.4 °C 3.6 °C, 2022 0.8 °C, 2014
Max 1hr Hum Rise 8% 06:45 9% 15%, 2023 1%, 2014
Max 10m Temp Fall 0.5 °C 06:22 0.4 °C 1.1 °C, 2023 0.2 °C, 2014
Max 1hr Temp Fall 1.1 °C 06:52 1.5 °C 2.9 °C, 2023 0.8 °C, 2016
Max 1hr Hum Fall 10% 12:57 12% 18%, 2019 2%, 2014
Max 10m Wind Speed 16.8 mph 23:09 10.0 mph 16.8 mph, 2018 4.0 mph, 2022
Minimum Feels-like 20.4 °C 00:10 13.9 °C 20.4 °C, 2018 7.3 °C, 2012
Maximum Feels-like 24.7 °C 14:52 23.7 °C 27.3 °C, 2024 17.3 °C, 2012
Mean Feels-like 22.5 °C 18.9 °C 22.5 °C, 2018 13.0 °C, 2012
Air-frost Hrs 0 hrs 0 hrs 0 hrs, 2009 0 hrs, 2009
Measure Value (anomaly) Month cumul. Record High Record Low
Temperature Range 3.9 °C (-3.2) 8.5 °C (+0.8) 10.8 °C (+3.7), 2015 3.3 °C (-3.8), 2014
Humidity Range 20% 37% 56%, 2019 4%, 2014
Pressure Range 15 hPa 5 hPa 15 hPa, 2018 2 hPa, 2022
Measure Value [% of max] Month cumul. Record High Record Low
Sun Hours 0.7 [6%]110 hrs (110%) [47%] 11.2 [100%], 2019 0 [0%], 2016
Wet Hours 2
[Mean rain rate: 0.5 mm/h]		10 hrs (37%) [2.1%] 10, 2023 0, 2009
Cloud Cover Overcast with periods of Mostly Cloudy
Events None
Comments am Rain spells
Extra Comments
Issues None known
Observer Absent? Yes - observations may be unreliable
Pond Temperature @ Hampstead Heath 0.0 °C
Notes
Detailed daily weather report for Hampstead nw3 in London on 20th September 2018.
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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