September Weather in London, United States

Last updated: June 24, 2025

In September, the average temperature in London, United States is a pleasant 22°C (72°F). However, it can swing from a cool 8°C (46°F) to a sizzling 36°C (97°F). Expect around 107 mm (4.2 in) of precipitation over 10 days, while the average humidity sits at a comfortable 67%.

September Temperature in London

In September in London, the average temperature is 22°C (72°F). Maximums can reach 36°C (97°F) and minimums can be as low as 8°C (46°F). It's a great time to visit for those who enjoy mild weather with occasional warm 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 22°C (72°F), with highs reaching up to 36°C (97°F) and lows dropping to around 8°C (46°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 107 mm (4.2 in) accumulated over a period of 10 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 107 mm (4.2 inches) of precipitation spread over approximately 10 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 67%. With an average temperature of 22°C (72°F), this humidity feels like a warm embrace, creating a tropical ambiance that can be both refreshing and slightly stifling for traveling.

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 67%, 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 9, which corresponds to a very high Exposure Category. The time to burn is just 15 minutes, so it's essential to take precautions. For detailed information, you can check 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 9, 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	3°C (38°F)	98 mm (3.9 inches)	88%	moderate
February Weather	6°C (43°F)	179 mm (7.0 inches)	88%	high
March Weather	10°C (49°F)	134 mm (5.3 inches)	87%	high
April Weather	14°C (57°F)	134 mm (5.3 inches)	84%	very high
May Weather	20°C (67°F)	126 mm (5.0 inches)	84%	extreme
June Weather	23°C (73°F)	141 mm (5.5 inches)	83%	extreme
July Weather	25°C (78°F)	109 mm (4.3 inches)	79%	extreme
August Weather	24°C (76°F)	123 mm (4.8 inches)	66%	very high
September Weather	22°C (72°F)	107 mm (4.2 inches)	67%	very high
October Weather	16°C (61°F)	120 mm (4.7 inches)	76%	high
November Weather	8°C (46°F)	76 mm (3.0 inches)	89%	moderate
December Weather	6°C (43°F)	135 mm (5.3 inches)	88%	moderate