September is one of the warmer months of the year in London, with average highs near 23°C and lows around 12°C (mean 17.5°C). It is a relatively wet time of year, averaging 71 mm of rainfall and 71% relative humidity across the period.
September is one of the warmer months of the year in London. Across 45 years of records, the warmest September in London was 2024 — when the month averaged 20.6°C — while the coldest was 1993 at 14.4°C. Typical September days reach 23°C with nights near 12°C. The long-term trend is warming, about 0.9°C per decade.
September is a relatively wet time of year in London, averaging 71 mm of rainfall. The wettest September on record was 1986 with 190 mm, while the driest was 2023 at 20 mm.
Relative humidity in London during September averages 71%. The most humid September was 1992 at 79%, and the least humid was 2025 at 61%.
September receives about 4.3 kWh/m²/day of solar energy in London. The sunniest September was 2025 at 4.9 kWh/m²/day, and the cloudiest was 1993 at 3.2.
Average wind speed in London during September is 2.9 m/s. The windiest September was 2010 at 3.5 m/s, while the calmest was 2025 at 2.2 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 16.2°C | 16.5°C | 18.0°C | 18.3°C | 19.2°C | +3°C |
| Avg High | 21.5°C | 22.0°C | 23.6°C | 23.6°C | 25.0°C | +3.5°C |
| Avg Low | 11.0°C | 11.0°C | 12.3°C | 13.0°C | 13.3°C | +2.3°C |
| Avg Rain | 93 mm | 71 mm | 70 mm | 76 mm | 34 mm | -58 mm |
September temperatures in London have risen by about 3.4°C between 1981–1985 and 2021–2025.
September has ranged from a record low of -0.5°C (1993) to a record high of 34.6°C (2002).
Rainfall in September is a relatively wet time of year, averaging 71 mm, with a wettest year of 190 mm.
One of the best times to visit London
September is one of the best times to visit London. Expect days averaging 23°C and nights around 12°C (mean 17.5°C) — warmer than London's yearly average — with moderate rainfall (71 mm), so conditions are generally comfortable for sightseeing and outdoor plans.
| Year | Avg High | Avg Temp | Avg Low | Hottest Day | Coldest Day | Rainfall | Humidity | Wind | Solar |
|---|---|---|---|---|---|---|---|---|---|
| 2025 | 26.3°C | 19.8°C | 13.3°C | 30.4°C | 7.9°C | 28 mm | 61% | 2.2 m/s | 4.9 |
| 2024 🔥 | 26.5°C | 20.6°C | 14.7°C | 30.5°C | 8.8°C | 24 mm | 64% | 2.7 m/s | 4.4 |
| 2023 | 25.1°C | 19.3°C | 13.4°C | 32.8°C | 8.3°C | 20 mm | 68% | 2.5 m/s | 4.3 |
| 2022 | 24.3°C | 18.7°C | 13.1°C | 31.9°C | 5.2°C | 26 mm | 67% | 2.7 m/s | 4.1 |
| 2021 | 24.2°C | 18.7°C | 13.1°C | 29.7°C | 6.8°C | 76 mm | 69% | 3.3 m/s | 4.5 |
| 2020 | 23.8°C | 17.9°C | 12.1°C | 29.6°C | 3.1°C | 31 mm | 69% | 3.3 m/s | 4.3 |
| 2019 | 23.9°C | 18.7°C | 13.5°C | 28.4°C | 9.3°C | 104 mm | 77% | 2.9 m/s | 4.2 |
| 2018 | 24.3°C | 19.4°C | 14.5°C | 32.3°C | 7.0°C | 86 mm | 76% | 2.9 m/s | 3.9 |
| 2017 | 24.4°C | 18.8°C | 13.2°C | 32.1°C | 5.8°C | 75 mm | 73% | 2.4 m/s | 4.6 |
| 2016 | 25.9°C | 20.2°C | 14.6°C | 32.8°C | 8.7°C | 51 mm | 68% | 2.9 m/s | 4.6 |
| 2015 | 25.3°C | 19.9°C | 14.6°C | 31.7°C | 8.4°C | 72 mm | 72% | 2.6 m/s | 4.4 |
| 2014 | 22.2°C | 17.0°C | 11.7°C | 29.8°C | 5.0°C | 95 mm | 76% | 2.7 m/s | 4.3 |
| 2013 | 22.1°C | 16.6°C | 11.1°C | 32.4°C | 4.4°C | 80 mm | 74% | 2.7 m/s | 4.3 |
| 2012 | 22.0°C | 16.8°C | 11.6°C | 30.8°C | 5.4°C | 81 mm | 71% | 2.8 m/s | 4.3 |
| 2011 | 23.0°C | 17.9°C | 12.9°C | 33.5°C | 6.6°C | 60 mm | 74% | 3 m/s | 3.7 |
| 2010 | 22.7°C | 17.3°C | 11.9°C | 32.2°C | 7.4°C | 56 mm | 68% | 3.5 m/s | 3.9 |
| 2009 | 24.0°C | 18.3°C | 12.7°C | 27.7°C | 6.4°C | 27 mm | 67% | 2.8 m/s | 4.4 |
| 2008 | 24.2°C | 18.4°C | 12.6°C | 33.1°C | 8.1°C | 62 mm | 71% | 2.7 m/s | 4.3 |
| 2007 | 25.4°C | 19.3°C | 13.2°C | 33.0°C | 7.2°C | 27 mm | 66% | 2.7 m/s | 4.7 |
| 2006 | 21.2°C | 16.2°C | 11.3°C | 27.7°C | 4.9°C | 69 mm | 75% | 3.3 m/s | 3.6 |
| 2005 | 25.6°C | 19.4°C | 13.3°C | 31.5°C | 6.6°C | 53 mm | 69% | 3 m/s | 4.6 |
| 2004 | 24.8°C | 18.9°C | 12.9°C | 29.0°C | 7.0°C | 42 mm | 70% | 2.7 m/s | 4.7 |
| 2003 | 22.2°C | 16.8°C | 11.4°C | 29.4°C | 4.0°C | 114 mm | 71% | 3.2 m/s | 4.4 |
| 2002 | 26.0°C | 20.1°C | 14.3°C | 34.6°C | 7.3°C | 91 mm | 66% | 2.7 m/s | 4.7 |
| 2001 | 21.8°C | 16.3°C | 10.7°C | 29.2°C | 3.4°C | 95 mm | 71% | 3 m/s | 4.4 |
| 2000 | 21.2°C | 16.1°C | 10.9°C | 31.4°C | 1.5°C | 119 mm | 76% | 3.2 m/s | 4.2 |
| 1999 | 24.0°C | 18.0°C | 12.0°C | 32.1°C | 3.0°C | 77 mm | 65% | 2.9 m/s | 4.7 |
| 1998 | 25.0°C | 19.2°C | 13.4°C | 31.4°C | 7.1°C | 34 mm | 66% | 2.8 m/s | 4.5 |
| 1997 | 22.2°C | 16.8°C | 11.3°C | 27.9°C | 3.3°C | 55 mm | 72% | 3.2 m/s | 4.2 |
| 1996 | 21.6°C | 16.7°C | 11.8°C | 30.9°C | 4.4°C | 136 mm | 75% | 3 m/s | 3.7 |
| 1995 | 21.7°C | 15.5°C | 9.3°C | 30.0°C | 3.2°C | 31 mm | 65% | 2.9 m/s | 4.4 |
| 1994 | 22.7°C | 16.9°C | 11.0°C | 28.7°C | 6.1°C | 36 mm | 70% | 3 m/s | 4.5 |
| 1993 ❄️ | 19.3°C | 14.4°C | 9.4°C | 28.2°C | -0.5°C | 96 mm | 73% | 3.1 m/s | 3.2 |
| 1992 | 20.2°C | 15.3°C | 10.3°C | 26.2°C | 3.5°C | 118 mm | 79% | 3.2 m/s | 4.2 |
| 1991 | 22.0°C | 16.2°C | 10.4°C | 31.0°C | 2.1°C | 33 mm | 64% | 2.9 m/s | 4.2 |
| 1990 | 21.6°C | 16.1°C | 10.6°C | 28.8°C | 3.6°C | 98 mm | 75% | 2.9 m/s | 4 |
| 1989 | 22.1°C | 16.5°C | 10.9°C | 28.6°C | 0.1°C | 71 mm | 72% | 2.8 m/s | 4 |
| 1988 | 22.1°C | 16.6°C | 11.0°C | 27.7°C | 7.2°C | 66 mm | 72% | 3.1 m/s | 4.3 |
| 1987 | 21.8°C | 16.8°C | 11.8°C | 28.1°C | 6.8°C | 64 mm | 77% | 2.5 m/s | 3.9 |
| 1986 🌧️ | 21.5°C | 16.1°C | 10.6°C | 26.5°C | 3.2°C | 190 mm | 78% | 2.9 m/s | 4 |
| 1985 | 22.5°C | 17.1°C | 11.8°C | 30.0°C | 3.8°C | 48 mm | 74% | 2.8 m/s | 4.4 |
| 1984 | 19.9°C | 14.8°C | 9.8°C | 27.5°C | 3.9°C | 97 mm | 76% | 2.7 m/s | 4.2 |
| 1983 | 23.2°C | 17.2°C | 11.3°C | 32.3°C | 3.0°C | 69 mm | 68% | 2.9 m/s | — |
| 1982 | 21.0°C | 15.8°C | 10.5°C | 29.2°C | 4.6°C | 101 mm | 76% | 2.5 m/s | — |
| 1981 | 19.5°C | 15.2°C | 10.9°C | 26.5°C | 3.2°C | 128 mm | 79% | 3 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 23°C with lows near 12°C (mean 17.5°C), based on 45 years of NASA POWER data.
September averages 71 mm of rainfall in London, a relatively wet time of year. The wettest on record was 190 mm in 1986.
The hottest September reached 34.6°C in 2002. The coldest dipped to -0.5°C in 1993.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 3.4°C. Daytime highs moved from 21.2°C to 25.3°C and overnight lows from 10.9°C to 13.5°C over the same span.
September is one of the warmer months of the year in London and a relatively wet time of year, so plan for around 23°C daytime highs and 12°C at night.
Not quite — September is the 9th coolest month in London, averaging 17.5°C.
For September in London, pack light layers you can adjust through the day, with typical highs of 23°C and lows of 12°C. Bring an umbrella or light rain jacket too.
Relative humidity in September averages 71% — moderately humid.
Average wind speed in September is 2.9 m/s. The windiest September on record averaged 3.5 m/s (2010).
The wettest September on record was 1986 with 190 mm. On average, September sees 71 mm.
All figures are derived from NASA POWER (Prediction Of Worldwide Energy Resources), based on MERRA-2 satellite reanalysis, covering 1981–2025.
Explore how the weather in London behaves each September, based on 45 years of NASA POWER climate data from 1981 to 2025. This page breaks down average temperatures, rainfall, humidity, wind and solar radiation for September specifically, along with year-by-year records and how the month has changed over the decades.
