September Weather in London, United States

Last updated: June 24, 2025

In London, United States, the average temperature in September hovers around 20°C (69°F), with a minimum dipping to 5°C (41°F) and a maximum reaching up to 34°C (94°F). Expect an average precipitation of 94 mm (3.7 in) spread over 8 days, with an average humidity of 73%. Prepare for a month of warm days and occasional showers!

September Temperature in London

In September in London, the average temperature is 20°C (69°F). Maximums can reach 34°C (94°F), while minimums can drop as low as 5°C (41°F). This makes London a suitable destination for travelers looking to experience mild weather with the possibility of warmer days.

September Weather in London: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in London, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In London, September typically has an average temperature of 20°C (69°F), with highs reaching up to 34°C (94°F) and lows dropping to around 5°C (41°F).

Data source: Temperature data for London generated using information from the Copernicus Climate Change Service.

September Precipitation in London

In London in September, the precipitation amount is 94 mm (3.7 in) over the course of 8 days.

September Precipitation Trends in London

The chart displays monthly precipitation patterns in London, with values for each month alongside September’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how September’s conditions compare to those of other months. In London, September typically receives around 94 mm (3.7 inches) of precipitation spread over approximately 8 days.

Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.

Choose your preferred precipitation unit

Millimeters (mm) Inches (in)

September Humidity in London

In London in September humidity is 73%. With an average temperature of 20°C (69°F), this humidity feels like a warm embrace, making travel slightly sticky but ultimately comfortable as long as you stay hydrated and take breaks in the shade.

September Average Humidity in London

This chart illustrates the average monthly humidity levels in London, with September’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In September, average humidity in London is approximately 73%, offering insight into how humid the weather typically is during this month.

Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in London

In London in September, the maximum UV index is 8, which corresponds to a very high Exposure Category. This means that the time to burn is only 15 minutes. For more detailed information, you can refer to the Hourly UV Index in London.

Maximum UV Index Levels in London for September

The chart shows the monthly maximum UV Index (UVI) for London in September, representing the highest UV radiation level. The UVI measures the intensity of ultraviolet radiation from the sun, indicating the potential risk of sunburn and UV-related health issues. In September, the maximum UV index in London typically reaches 8, which falls under the very high exposure category.

Data source: London September UVI data generated using information from the Copernicus Climate Change Service.

UV Risk Categories

Extreme (11+): Avoid the sun, stay in shade.
Very High (8-10): Limit sun exposure.
High (6-7): Use SPF 30+ and protective clothing.
Moderate (3-5): Midday shade recommended.
Low (0-2): No protection needed.

How September Weather in London Compares to Other Months

Weather in London varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in London, focusing on differences in temperature, rainfall, humidity, and UV levels.

This table compares monthly weather conditions in London, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
	Temperature	Precipitation	Humidity	UV
January Weather	-1°C (30°F)	75 mm (3.0 inches)	88%	moderate
February Weather	1°C (34°F)	104 mm (4.1 inches)	88%	moderate
March Weather	6°C (42°F)	108 mm (4.2 inches)	87%	high
April Weather	11°C (52°F)	111 mm (4.4 inches)	85%	very high
May Weather	17°C (64°F)	131 mm (5.1 inches)	81%	very high
June Weather	22°C (72°F)	134 mm (5.3 inches)	82%	very high
July Weather	24°C (75°F)	120 mm (4.7 inches)	81%	very high
August Weather	23°C (73°F)	99 mm (3.9 inches)	73%	very high
September Weather	20°C (69°F)	94 mm (3.7 inches)	73%	very high
October Weather	14°C (58°F)	95 mm (3.7 inches)	78%	high
November Weather	5°C (42°F)	95 mm (3.7 inches)	89%	moderate
December Weather	2°C (36°F)	95 mm (3.8 inches)	87%	moderate