Daily Report for 20th September 2017
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| Measure | Value (anomaly) | Time | Month cumul. | Record High | Record Low |
| Minimum Temperature | 9.1 °C (-2.0) | 03:27 | 10.2 °C (-1.8) | 16.7 °C (+5.6), 2018 | 8.4 °C (-2.7), 2015 |
| Maximum Temperature | 17.6 °C (-0.6) | 13:32 | 18.1 °C (-1.7) | 23.9 °C (+5.7), 2020 | 17.3 °C (-0.9), 2012 |
| Mean Temperature | 13.8 °C (-1.3) | 14.0 °C (-1.8) | 18.6 °C, 2018 | 13.2 °C, 2012 | |
| Minimum Humidity | 70% | 13:38 | 59% | 92%, 2014 | 40%, 2019 |
| Maximum Humidity | 96% | 05:48 | 92% | 96%, 2014 | 78%, 2012 |
| Mean Humidity | 83% | 79% | 94%, 2014 | 62%, 2012 | |
| Minimum Pressure | 1016 hPa | 23:30 | 1007 hPa | 1026 hPa, 2022 | 994 hPa, 2023 |
| Maximum Pressure | 1022 hPa | 00:00 | 1014 hPa | 1031 hPa, 2019 | 1005 hPa, 2023 |
| Mean Pressure | 1019 hPa | 1011 hPa | 1027 hPa, 2022 | 1000 hPa, 2023 | |
| Mean Wind Speed | 4.7 mph (+0.8) | 4.6 mph (+0.7) | 10.5 mph, 2023 | 1.2 mph, 2022 | |
| Maximum Wind Speed | 12.1 mph | 17:40 | 13.0 mph | 23.2 mph, 2023 | 5.8 mph, 2022 |
| Maximum Gust | 18.4 mph | 17:02 | 20.4 mph | 35.7 mph, 2023 | 9.2 mph, 2013 |
| Mean Wind Direction | n/a | WSW | N, 2021 | N, 2009 | |
| Rainfall | 0.0 mm | 33.4 mm (100%) | 29.3 mm, 2014 | 0.0 mm, 2009 | |
| Maximum Hourly Rain | n/a | 0.9 mm | 18.7 mm, 2014 | 0.7 mm, 2018 | |
| Maximum 10-min Rain | n/a | 0.5 mm | 7.9 mm, 2014 | 0.2 mm, 2018 | |
| Maximum Rain Rate | n/a | 8 mm/h | 126 mm/h, 2014 | 0.8 mm/h, 2018 | |
| Minimum Dew Point | 8.0 °C | 03:17 | 7.8 °C | 14.3 °C, 2018 | 3.0 °C, 2012 |
| Maximum Dew Point | 12.9 °C | 10:59 | 12.6 °C | 17.1 °C, 2014 | 8.3 °C, 2012 |
| Mean Dew Point | 10.9 °C | 10.1 °C | 15.6 °C, 2014 | 5.9 °C, 2012 | |
| Measure | Value | Time | Month cumul. | Record High | Record Low |
| Night Minimum (21-09) | 8.2 °C | 22:06 | 10.3 °C | 16.9 °C, 2023 | 8.2 °C, 2017 |
| Day Maximum (09-21) | 17.6 °C | 13:32 | 18.1 °C | 23.9 °C, 2020 | 17.3 °C, 2012 |
| Max 10m Temp Rise | 0.6 °C | 08:50 | 0.6 °C | 0.8 °C, 2022 | 0.3 °C, 2011 |
| Max 1hr Temp Rise | 2.9 °C | 09:11 | 2.1 °C | 3.6 °C, 2022 | 0.8 °C, 2014 |
| Max 1hr Hum Rise | 6% | 14:47 | 11% | 15%, 2023 | 1%, 2014 |
| Max 10m Temp Fall | 0.4 °C | 18:39 | 0.7 °C | 1.1 °C, 2023 | 0.2 °C, 2014 |
| Max 1hr Temp Fall | 1.3 °C | 19:29 | 1.9 °C | 2.9 °C, 2023 | 0.8 °C, 2016 |
| Max 1hr Hum Fall | 9% | 09:11 | 10% | 18%, 2019 | 2%, 2014 |
| Max 10m Wind Speed | 9.4 mph | 17:42 | 9.6 mph | 16.8 mph, 2018 | 4.0 mph, 2022 |
| Minimum Feels-like | 7.3 °C | 03:44 | 10.0 °C | 20.4 °C, 2018 | 7.3 °C, 2012 |
| Maximum Feels-like | 20.1 °C | 13:23 | 20.1 °C | 27.3 °C, 2024 | 17.3 °C, 2012 |
| Mean Feels-like | 15.4 °C | 15.3 °C | 22.5 °C, 2018 | 13.0 °C, 2012 | |
| Air-frost Hrs | 0 hrs | 0 hrs | 0 hrs, 2009 | 0 hrs, 2009 | |
| 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 | 8.5 °C (+1.4) | 8.0 °C | 10.8 °C, 2015 | 3.3 °C, 2014 | |
| Humidity Range | 26% | 33% | 56%, 2019 | 4%, 2014 | |
| Pressure Range | 6 hPa | 7 hPa | 15 hPa, 2018 | 2 hPa, 2022 | |
| Observation | Detail | ||||
| Sun Hours | 2 hrs [18%] | ||||
| Wet Hours | 0 hrs | ||||
| Cloud Cover | Mostly Cloudy with periods of Partly Cloudy | ||||
| Events | None | ||||
| Comments | - | ||||
| Observer Absent? | Yes - observations may be unreliable | ||||
| Pond Temperature | 0.0 °C | ||||
- Notes
- Detailed daily weather report for Hampstead, NW3, London on 20th September 2017. 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
