Daily Report for 23rd December 2009

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Measure Value (anomaly) Time Month cumul. Record High Record Low
Minimum Temperature -3.9 °C (-7.3) 08:30 1.6 °C (-2.1) 10.8 °C (+7.4), 2014 -3.9 °C (-7.3), 2009
Maximum Temperature 3.8 °C (-3.9) 20:25 6.1 °C (-2.2) 12.9 °C (+5.2), 2012 1.9 °C (-5.8), 2010
Mean Temperature -0.5 °C (-5.6) 3.9 °C (-2.1) 11.7 °C, 2014 -0.5 °C, 2009
Minimum Humidity 98% 12:00 82% 98%, 2009 63%, 2015
Maximum Humidity 98% 12:00 97% 98%, 2009 76%, 2014
Mean Humidity 98% 91% 98%, 2009 72%, 2014
Minimum Pressure 989 hPa 18:59 1004 hPa 1030 hPa, 2017 978 hPa, 2013
Maximum Pressure 991 hPa 08:43 1012 hPa 1037 hPa, 2017 991 hPa, 2009
Mean Pressure 990 hPa 1008 hPa 1033 hPa, 2017 990 hPa, 2009
Mean Wind Speed 1.5 mph (-3.6) 4.4 mph (-0.7) 12.1 mph, 2013 1.5 mph, 2009
Maximum Wind Speed 8.1 mph 10.8 mph 31.7 mph, 2013 8.1 mph, 2009
Maximum Gust 13.8 mph 20:28 16.2 mph 47.6 mph, 2013 13.8 mph, 2009
Mean Wind Direction SE
Rainfall 5.7 mm 55.7 mm (132%) 15.2 mm, 2013
Maximum Hourly Rain n/a 20:50 6.3, 2022
Maximum 10-min Rain n/a 19:51 2, 2022
Maximum Rain Rate n/a 20:50 20, 2011
Minimum Dew Point -4.2 °C 08:30 -0.0 °C 7.3 °C, 2022 -4.8 °C, 2010
Maximum Dew Point 3.5 °C 20:25 5.3 °C 12.6 °C, 2012 -1.9 °C, 2010
Mean Dew Point -0.8 °C 2.6 °C 9.8 °C, 2020 -3.0 °C, 2010
Measure Value Time Month cumul. Record High Record Low
Night Minimum (21-09) -3.9 °C 2.3 °C 11.8 °C, 2012 -3.9 °C, 2009
Day Maximum (09-21) 3.8 °C 5.9 °C 12.8 °C, 2014 1.9 °C, 2010
Max 10m Temp Rise 0.4 °C 10:15 0.4 °C 0.5 °C, 2022 0.1 °C, 2011
Max 1hr Temp Rise 1.5 °C 12:30 1.0 °C 1.8 °C, 2022 0.3 °C, 2012
Max 1hr Hum Rise 0% 00:59 4% 9%, 2011 0%, 2009
Max 10m Temp Fall 0.8 °C 20:38 0.4 °C 1.4 °C, 2018 0.1 °C, 2012
Max 1hr Temp Fall 2.1 °C 21:23 1.0 °C 4.2 °C, 2018 0.3 °C, 2013
Max 1hr Hum Fall 0% 00:59 5% 8%, 2014 0%, 2009
Max 10m Wind Speed 7.2 mph 20:43 7.8 mph 23.2 mph, 2013 7.2 mph, 2009
Minimum Feels-like -3.9 °C 07:54 -1.6 °C 10.8 °C, 2014 -6.8 °C, 2010
Maximum Feels-like 3.8 °C 20:23 6.5 °C 15.5 °C, 2012 -1.0 °C, 2010
Mean Feels-like -1.2 °C 2.8 °C 12.4 °C, 2012 -3.5 °C, 2010
Air-frost Hrs 13 hrs 4 hrs 13 hrs, 2009 0 hrs, 2011
Measure Value (anomaly) Month cumul. Record High Record Low
Temperature Range 7.7 °C (+3.4) 4.6 °C (-0.0) 7.7 °C (+3.4), 2009 2.0 °C (-2.3), 2014
Humidity Range 0% 14% 27%, 2015 0%, 2009
Pressure Range 2 hPa 8 hPa 34 hPa, 2013 2 hPa, 2009
Measure Value [% of max] Month cumul. Record High Record Low
Sun Hours 2 [29%]64 hrs (133%) [39%] 5.3 [76%], 2015 0 [0%], 2010
Wet Hours 6
[Mean rain rate: 1.0 mm/h]
65 hrs (140%) [12%] 13, 2013 0, 2010
Cloud Cover not available
Events Lying Snow (at 09z): ~2 cm
Air Frost
Comments Lying Snow: 2cm; 17-00 Light-Heavy Rain/Drizzle
Extra Comments 23rd: Hard Frost/Rime due to light am freezing fog; 22nd-25th: RHeavy at 98% from 20z on 22nd to 12z on 25th (64 hrs)
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 23rd December 2009.
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.
View monthly summary

Daily Graph of Conditions

daygraph daygraph 2 daygraph-wdir

Webcam Summary of Cloud Conditions


Webcam summary not available for this day

Wind rose