September in London averages a daily high of 22.4°C with nights around 11.2°C. Expect roughly 9.5 wet days totalling 77.2mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit London is May–September.
Based on LONDON CS, ON CA (8.7km), 1995–2024. 20 years of September data.