Weather in London in September

Daylight on the 15th: 12 h 40 min
Average high: 20 °C (68 °F)
Average low: 10 °C (50 °F)
Precipitation: 46 mm

In September, the area around London averages daytime highs of 20 °C (68 °F) and night-time lows of 10 °C (50 °F). Days are mild; a light jacket covers most of it.

Temperature

Compared with August, September is cooler by 3 °C in daytime highs, and October is cooler by 4 °C than September. The daily average is 15 °C (58 °F).

Precipitation, humidity and wind

Precipitation averages about 46 mm over the month, with 10 days of at least 1 mm. Expect some wet days, but not every day.

Relative humidity averages 81 % and wind at 2 m about 3.1 m/s.

Daylight

On 15 September the sun rises at 06:36 and sets at 19:16 local time, for 12 h 40 min of daylight, 117 minutes less than a month earlier.

About these numbers

The figures are 2011-2020 averages for the grid cell around London from the NASA POWER project, a model based data set. They describe the area rather than one weather station, and a single year can differ.

Month by month

Month	High	Low	Precipitation
January	7 °C	2 °C	67 mm
February	8 °C	2 °C	51 mm
March	11 °C	3 °C	48 mm
April	14 °C	4 °C	43 mm
May	17 °C	7 °C	50 mm
June	20 °C	10 °C	66 mm
July	23 °C	12 °C	57 mm
August	22 °C	12 °C	66 mm
September	20 °C	10 °C	46 mm
October	15 °C	8 °C	75 mm
November	11 °C	5 °C	71 mm
December	8 °C	3 °C	83 mm

Questions

How warm is London in September?

Average highs of 20 °C (68 °F) and lows of 10 °C (50 °F) (2011-2020 averages).

Does it rain a lot in London in September?

About 46 mm over the month, on 10 days with at least 1 mm.

Travel data for United Kingdom

Sources

NASA Langley Research Center POWER Project, funded through the NASA Earth Science Directorate Applied Science Program (2026-09-22)
Computed from the city coordinates with the NOAA solar position equations
IANA tz database
Wikidata, CC0 (2026-09-22)