Daily Report for 18th September 2017

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Measure Value (anomaly) Time Month cumul. Record High Record Low
Minimum Temperature 10.0 °C (-1.3) 04:34 10.4 °C (-1.7) 17.6 °C (+6.3), 2018 6.8 °C (-4.5), 2010
Maximum Temperature 16.6 °C (-1.9) 14:39 18.4 °C (-1.5) 24.2 °C (+5.7), 2014 15.3 °C (-3.2), 2013
Mean Temperature 12.7 °C (-1.6) 14.2 °C (-1.6) 19.2 °C, 2018 11.8 °C, 2011
Minimum Humidity 61% 14:41 58% 74%, 2015 37%, 2012
Maximum Humidity 95% 04:58 92% 96%, 2014 82%, 2012
Mean Humidity 83% 78% 85%, 2015 60%, 2012
Minimum Pressure 1016 hPa 03:45 1006 hPa 1029 hPa, 2019 995 hPa, 2013
Maximum Pressure 1020 hPa 23:15 1013 hPa 1032 hPa, 2019 1008 hPa, 2011
Mean Pressure 1017 hPa 1010 hPa 1030 hPa, 2019 1003 hPa, 2023
Mean Wind Speed 2.8 mph (-1.1) 4.8 mph (+0.9) 9.4 mph, 2018 1.6 mph, 2016
Maximum Wind Speed 9.6 mph 14:59 13.4 mph 21.3 mph, 2023 7.5 mph, 2019
Maximum Gust 17.3 mph 15:00 21.1 mph 34.6 mph, 2023 10.0 mph, 2011
Mean Wind Direction NNW
Rainfall 2.0 mm 31.9 mm (106%) 8.2 mm, 2023
Maximum Hourly Rain 1.3 mm 23:45 7.9 mm, 2023
Maximum 10-min Rain 0.4 mm 23:45 3.9 mm, 2023
Maximum Rain Rate 2.6 mm/h 23:45 30 mm/h, 2023
Minimum Dew Point 7.7 °C 17:49 7.9 °C 13.9 °C, 2014 0.2 °C, 2012
Maximum Dew Point 11.7 °C 12:04 12.7 °C 17.7 °C, 2014 7.5 °C, 2010
Mean Dew Point 9.7 °C 10.1 °C 15.2 °C, 2014 5.4 °C, 2010
Measure Value Time Month cumul. Record High Record Low
Night Minimum (21-09) 10.0 °C 04:34 10.6 °C 17.6 °C, 2018 6.8 °C, 2010
Day Maximum (09-21) 16.6 °C 14:39 18.4 °C 24.2 °C, 2014 15.3 °C, 2013
Max 10m Temp Rise 0.7 °C 10:14 0.6 °C 0.9 °C, 2019 0.3 °C, 2016
Max 1hr Temp Rise 2.0 °C 10:53 2.0 °C 3.9 °C, 2019 1.0 °C, 2022
Max 1hr Hum Rise 11% 15:41 12% 14%, 2021 4%, 2016
Max 10m Temp Fall 0.7 °C 15:00 0.7 °C 1.0 °C, 2023 0.2 °C, 2016
Max 1hr Temp Fall 1.8 °C 15:37 1.8 °C 2.1 °C, 2019 0.8 °C, 2016
Max 1hr Hum Fall 16% 14:41 10% 16%, 2017 6%, 2015
Max 10m Wind Speed 5.9 mph 13:11 9.8 mph 16.3 mph, 2023 5.1 mph, 2019
Minimum Feels-like 10.9 °C 04:29 10.4 °C 19.1 °C, 2018 5.2 °C, 2010
Maximum Feels-like 18.1 °C 14:33 20.3 °C 28.5 °C, 2024 15.7 °C, 2013
Mean Feels-like 13.8 °C 15.5 °C 22.9 °C, 2014 11.7 °C, 2010
Air-frost Hrs 0 hrs 0 hrs 0 hrs, 2009 0 hrs, 2009
Measure Value (anomaly) Month cumul. Record High Record Low
Temperature Range 6.6 °C (-0.6) 8.0 °C (+0.2) 11.4 °C (+4.2), 2019 4.4 °C (-2.8), 2018
Humidity Range 34% 33% 45%, 2012 18%, 2015
Pressure Range 4 hPa 7 hPa 19 hPa, 2012 2 hPa, 2021
Measure Value [% of max] Month cumul. Record High Record Low
Sun Hours 3 [27%]76 hrs (83%) [36%] 11.3 [100%], 2019 0.2 [2%], 2016
Wet Hours 2.5
[Mean rain rate: 0.8 mm/h]		32 hrs (130%) [7.4%] 3, 2023 0, 2009
Cloud Cover Mostly Cloudy with periods of Partly Cloudy
Events None
Comments 11-16 brief Showers; 22- Rain
Extra Comments
Issues None known
Observer Absent? Yes - observations may be unreliable
Pond Temperature (Heath) 0.0 °C
Notes
Detailed daily weather report for Hampstead nw3 in London on 18th September 2017.
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

day graph

Webcam Summary of Cloud Conditions

daycamsumLarge resolution version

Wind rose