Climatological averages, historical records, packing tips and best time to visit London during September. Met Office / ECMWF reanalysis 1991-2020.
Reference values based on 1991-2020 Met Office / ECMWF climatology. Year-to-year variation can be significant.
| Metric | Value | Date |
|---|---|---|
| All-time high | 40.2 °C | July 2022 |
| Heatwave record | 37.9 °C | August 2003 |
| All-time low | -13.2 °C | January 1962 |
| 24h rainfall | 75 mm | September 1968 |
Official records (Met Office). Secondary stations may have more extreme readings.
In September, London typically shows cooling with golden parks. The average high temperature is around 20°C and the average low around 12°C, with monthly rainfall of 49 mm spread over roughly 9 rain days and about 142 hours of sunshine. Average relative humidity stands at 79% and wind speed averages 13 km/h.
The local calendar in September is shaped by Open House London, so checking the forecast a few days in advance is worth it before any outdoor activity. Averages give a general picture but extreme events can vary widely: in September, London has recorded both unusually warm spells and cold incursions across recent decades.
For a typical stay we recommend light jacket and umbrella. UV protection is sensible on sunny days, even in a mild winter month, and a closed-toe waterproof shoe helps on damp days. For multi-day trips bring thin layers that you can combine through the day.
The first two weeks of September usually offer the best balance in London: moderate crowds, friendlier prices and weather that remains representative of the month. Late September starts showing features of the transition to the next month. Use our custom historical lookup to check the actual values for the exact year you plan to travel.
Of the twelve months, September is the 4th warmest in London and the 10th wettest. It collects 51 mm, 7 % of the whole year’s rain, spread over 9.5 days with appreciable precipitation. The warmest month is July and the wettest is October.
Among the 10 international cities with an ERA5-Land series on this site, in September London is the 8th warmest, with a mean maximum of 18.9 °C, and the 8th wettest. The wettest of them that month is Mexico City, with 204 mm against London’s 51 mm.
ERA5-Land reanalysis from the Copernicus Climate Data Store (CC-BY licence), 30 complete years, 1995 to 2024. AEMET publishes normals for Spanish stations only, so the figures for London come from the global series. Sources and methodology → · Forecast for London →
