Daily Report for 20th December 2009
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| Measure | Value (anomaly) | Time | Month cumul. | Record High | Record Low |
| Minimum Temperature | -3.3 °C (-6.7) | 09:28 | 2.2 °C (-1.5) | 9.4 °C (+6.0), 2015 | -7.2 °C (-10.6), 2010 |
| Maximum Temperature | 1.1 °C (-6.6) | 14:29 | 6.7 °C (-1.7) | 14.6 °C (+6.9), 2015 | 0.3 °C (-7.4), 2010 |
| Mean Temperature | -0.4 °C (-6.7) | 4.6 °C (-1.6) | 12.2 °C, 2015 | -3.2 °C, 2010 | |
| Minimum Humidity | 73% | 14:22 | 81% | 96%, 2012 | 62%, 2014 |
| Maximum Humidity | 97% | 03:15 | 97% | 98%, 2012 | 80%, 2016 |
| Mean Humidity | 84% | 90% | 98%, 2012 | 75%, 2014 | |
| Minimum Pressure | 997 hPa | 19:44 | 1007 hPa | 1034 hPa, 2017 | 977 hPa, 2019 |
| Maximum Pressure | 1000 hPa | 00:07 | 1015 hPa | 1036 hPa, 2017 | 988 hPa, 2019 |
| Mean Pressure | 998 hPa | 1011 hPa | 1035 hPa, 2017 | 982 hPa, 2019 | |
| Mean Wind Speed | 4.9 mph (-0.2) | 4.7 mph (-0.4) | 8.1 mph, 2015 | 1.4 mph, 2021 | |
| Maximum Wind Speed | 10.7 mph | 11.2 mph | 20.1 mph, 2013 | 7.4 mph, 2021 | |
| Maximum Gust | 15.2 mph | 05:02 | 16.7 mph | 30.8 mph, 2013 | 11.5 mph, 2017 |
| Mean Wind Direction | n/a | SSE | WNW, 2023 | ENE, 2021 | |
| Rainfall | 2.0 mm | 44.0 mm (120%) | 21.7 mm, 2012 | 0.0 mm, 2013 | |
| Maximum Hourly Rain | n/a | 1.1 mm | 4.1 mm, 2012 | 0.5 mm, 2011 | |
| Maximum 10-min Rain | n/a | 0.2 mm | 1.2 mm, 2012 | 0.3 mm, 2011 | |
| Maximum Rain Rate | n/a | 0.3 mm/h | 9 mm/h, 2012 | 0.5 mm/h, 2011 | |
| Minimum Dew Point | -6.1 °C | 09:57 | 0.5 °C | 6.5 °C, 2015 | -9.3 °C, 2010 |
| Maximum Dew Point | 0.2 °C | 03:15 | 5.8 °C | 11.9 °C, 2022 | -0.4 °C, 2010 |
| Mean Dew Point | -2.8 °C | 3.1 °C | 8.4 °C, 2017 | -4.7 °C, 2010 | |
| Measure | Value | Time | Month cumul. | Record High | Record Low |
| Night Minimum (21-09) | -3.3 °C | 3.0 °C | 12.3 °C, 2015 | -7.2 °C, 2010 | |
| Day Maximum (09-21) | 1.1 °C | 6.5 °C | 13.0 °C, 2015 | 0.3 °C, 2010 | |
| Max 10m Temp Rise | 0.7 °C | 12:14 | 0.4 °C | 0.7 °C, 2009 | 0.2 °C, 2012 |
| Max 1hr Temp Rise | 2.1 °C | 13:03 | 0.9 °C | 2.6 °C, 2025 | 0.4 °C, 2021 |
| Max 1hr Hum Rise | 4% | 01:19 | 4% | 8%, 2018 | 1%, 2012 |
| Max 10m Temp Fall | 0.5 °C | 07:19 | 0.4 °C | 0.5 °C, 2009 | 0.1 °C, 2017 |
| Max 1hr Temp Fall | 1.4 °C | 07:20 | 0.9 °C | 1.7 °C, 2015 | 0.1 °C, 2017 |
| Max 1hr Hum Fall | 6% | 10:02 | 6% | 9%, 2013 | 2%, 2012 |
| Max 10m Wind Speed | 7.0 mph | 12:52 | 7.9 mph | 15.5 mph, 2013 | 5.3 mph, 2021 |
| Minimum Feels-like | -8.3 °C | 09:57 | -1.1 °C | 5.7 °C, 2015 | -10.2 °C, 2010 |
| Maximum Feels-like | 1.1 °C | 14:09 | 7.2 °C | 15.5 °C, 2015 | 0.3 °C, 2010 |
| Mean Feels-like | -3.0 °C | 3.3 °C | 12.5 °C, 2015 | -5.0 °C, 2010 | |
| Air-frost Hrs | 12 hrs | 3 hrs | 17 hrs, 2010 | 0 hrs, 2011 | |
| Minimum PM2.5 | n/a | 0.0 µg/m3 | 0.0 µg/m3, 2009 | 0.0 µg/m3, 2009 | |
| Maximum PM2.5 | n/a | 0.0 µg/m3 | n/a | n/a | |
| Mean PM2.5 | n/a | 0.0 µg/m3 | n/a | n/a | |
| Measure | Value (anomaly) | Month cumul. | Record High | Record Low | |
| Temperature Range | 4.4 °C (+0.1) | 4.4 °C | 7.9 °C, 2013 | 1.7 °C, 2021 | |
| Humidity Range | 24% | 16% | 29%, 2011 | 2%, 2012 | |
| Pressure Range | 3 hPa | 8 hPa | 13 hPa, 2012 | 2 hPa, 2010 | |
| Observation | Detail | ||||
| Sun Hours | 7 hrs [100%] | ||||
| Wet Hours | 2 hrs | ||||
| Cloud Cover | not available | ||||
| Events | Snowfall, Lying Snow, Air Frost | ||||
| Comments | 00-02 M Lying Sn: 3cmxx | ||||
| Observer Absent? | No | ||||
| Pond Temperature | 0.0 °C | ||||
- Notes
- Detailed daily weather report for Hampstead, NW3, London on 20th December 2009. Times of extremes use the midpoint of the longest continuous period at that value. Cumulative anomalies are relative to the expected value for the month-to-date. Sun and wet hours are derived from webcam/rainfall analysis and may be adjusted. Data should be viewed with appropriate caution.
Daily Graph of Conditions
Wind direction
Air pollution
Wind rose
Webcam Summary of Cloud Conditions
Webcam summary not available for this day.