Daily Report for 17th January 2023
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| Measure | Value (anomaly) | Time | Month cumul. | Record High | Record Low |
| Minimum Temperature | -4.9 °C (-7.9) | 07:41 | 4.7 °C (+1.6) | 6.6 °C (+3.6), 2014 | -5.5 °C (-8.5), 2013 |
| Maximum Temperature | 0.7 °C (-7.1) | 14:15 | 10.1 °C (+2.3) | 10.6 °C (+2.8), 2020 | 0.7 °C (-7.1), 2023 |
| Mean Temperature | -2.0 °C (-7.5) | 7.7 °C (+2.0) | 7.6 °C, 2011 | -2.0 °C, 2023 | |
| Minimum Humidity | 84% | 14:20 | 79% | 85%, 2011 | 49%, 2009 |
| Maximum Humidity | 93% | 09:56 | 93% | 98%, 2010 | 84%, 2017 |
| Mean Humidity | 89% | 87% | 93%, 2011 | 68%, 2009 | |
| Minimum Pressure | 988 hPa | 05:45 | 1000 hPa | 1035 hPa, 2022 | 987 hPa, 2014 |
| Maximum Pressure | 995 hPa | 23:49 | 1011 hPa | 1041 hPa, 2022 | 993 hPa, 2014 |
| Mean Pressure | 991 hPa | 1006 hPa | 1038 hPa, 2022 | 990 hPa, 2014 | |
| Mean Wind Speed | 1.7 mph (-3.5) | 7.9 mph (+2.7) | 10.1 mph, 2018 | 0.5 mph, 2017 | |
| Maximum Wind Speed | 7.9 mph | 22:46 | 18.2 mph | 22.1 mph, 2020 | 5.8 mph, 2017 |
| Maximum Gust | 12.7 mph | 22:44 | 29.4 mph | 34.6 mph, 2018 | 8.4 mph, 2017 |
| Mean Wind Direction | NW | ||||
| Rainfall | 0.0 mm | 50.5 mm (156%) | 16.1 mm, 2011 | ||
| Maximum Hourly Rain | n/a | 5, 2009 | |||
| Maximum 10-min Rain | n/a | 1.1, 2011 | |||
| Maximum Rain Rate | n/a | 15, 2011 | |||
| Minimum Dew Point | -6.3 °C | 07:35 | 2.8 °C | 5.3 °C, 2014 | -6.7 °C, 2013 |
| Maximum Dew Point | -1.6 °C | 13:42 | 8.1 °C | 9.4 °C, 2020 | -1.6 °C, 2023 |
| Mean Dew Point | -3.6 °C | 5.7 °C | 6.5 °C, 2011 | -3.6 °C, 2023 | |
| Measure | Value | Time | Month cumul. | Record High | Record Low |
| Night Minimum (21-09) | -4.9 °C | 07:40 | 6.0 °C | 8.6 °C, 2011 | -5.5 °C, 2013 |
| Day Maximum (09-21) | 0.7 °C | 14:16 | 10.0 °C | 9.0 °C, 2009 | 0.7 °C, 2023 |
| Max 10m Temp Rise | 0.4 °C | 11:27 | 0.4 °C | 0.6 °C, 2010 | 0.1 °C, 2011 |
| Max 1hr Temp Rise | 1.7 °C | 12:17 | 1.2 °C | 2.4 °C, 2013 | 0.4 °C, 2011 |
| Max 1hr Hum Rise | 4% | 17:08 | 6% | 7%, 2018 | 2%, 2016 |
| Max 10m Temp Fall | 0.3 °C | 16:14 | 0.4 °C | 0.9 °C, 2019 | 0.1 °C, 2016 |
| Max 1hr Temp Fall | 0.9 °C | 16:33 | 1.3 °C | 2.7 °C, 2022 | 0.3 °C, 2016 |
| Max 1hr Hum Fall | 6% | 12:25 | 6% | 13%, 2017 | 3%, 2016 |
| Max 10m Wind Speed | 5.1 mph | 22:50 | 13.6 mph | 17.1 mph, 2020 | 4.4 mph, 2017 |
| Minimum Feels-like | -7.3 °C | 08:50 | 1.1 °C | 2.8 °C, 2011 | -7.3 °C, 2023 |
| Maximum Feels-like | 0.7 °C | 14:03 | 10.6 °C | 11.6 °C, 2020 | 0.7 °C, 2023 |
| Mean Feels-like | -3.2 °C | 6.3 °C | 6.7 °C, 2011 | -3.2 °C, 2023 | |
| Air-frost Hrs | 21 hrs | 1 hrs | 21 hrs, 2023 | 0 hrs, 2010 | |
| Measure | Value (anomaly) | Month cumul. | Record High | Record Low | |
| Temperature Range | 5.6 °C (+0.8) | 5.5 °C (+0.7) | 8.5 °C (+3.7), 2012 | 1.9 °C (-2.9), 2014 | |
| Humidity Range | 9% | 14% | 39%, 2009 | 9%, 2023 | |
| Pressure Range | 7 hPa | 11 hPa | 19 hPa, 2010 | 2 hPa, 2012 | |
| Measure | Value [% of max] | Month cumul. | Record High | Record Low | |
| Sun Hours | 1 [13%] | 21 hrs (57%) [17%] | 7.6 [101%], 2022 | 0.1 [1%], 2011 | |
| Wet Hours | 0 | 56 hrs (152%) [14%] | 8, 2011 | , 2009 | |
| Cloud Cover | unknown | ||||
| Events | Air Frost | ||||
| Comments | blr | ||||
| Extra Comments | |||||
| Issues | None known | ||||
| Observer Absent? | No | ||||
| Pond Temperature (Heath) | 5.0 °C | ||||
- Notes
- 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 initially pulled from the official weather station at Heathrow, and later adjusted by hand to reflect local conditions based on webcam observations. Wet hrs are dervied algorithmically from rainfall data, though may be adjusted manually. Cloud cover and Events are manually reported, often with multi-week delays.
Daily Graph of Conditions
Webcam Summary of Cloud Conditions
Full resolution individual images at up-to 5 minute intervals