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September Weather in Mortlake, United Kingdom

Last updated: August 27, 2025

In Mortlake, United Kingdom, the average temperature in September hovers around 15°C (59°F), making it a pleasant time to explore. Expect slightly cooler nights with a minimum of 4°C (39°F), while daytime highs can reach up to 28°C (83°F). During this month, you might encounter around 45 mm (1.8 in) of precipitation spread over 10 days, so be sure to pack an umbrella! With an average humidity of 82%, the air can feel quite moist, contributing to the lush surroundings.

September Temperature in Mortlake

In September in Mortlake, the average temperature is 15°C (59°F), with maximums reaching 28°C (83°F) and minimums dropping as low as 4°C (39°F). This mild climate makes it an ideal time for travelers to explore and enjoy outdoor activities.

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

The chart illustrates September temperature patterns in Mortlake, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Mortlake, September typically has an average temperature of 15°C (59°F), with highs reaching up to 28°C (83°F) and lows dropping to around 4°C (39°F).
JanFebMarAprMayJunJulAugSepOctNovDec414345495562656459534643
Data source: Temperature data for Mortlake generated using information from the Copernicus Climate Change Service.
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The average of daily temperatures (24 hours) calculated across all days in the month.

September Precipitation in Mortlake

In Mortlake in September, the precipitation amount is 45 mm (1.8 in) spread over a duration of 10 days.

September Precipitation Trends in Mortlake

The chart displays monthly precipitation patterns in Mortlake, 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 Mortlake, September typically receives around 45 mm (1.8 inches) of precipitation spread over approximately 10 days.
JanFebMarAprMayJunJulAugSepOctNovDec545354336277647045845284
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Mortlake

In Mortlake in September, humidity is 82%. With an average temperature of 15°C (59°F), this humidity feels like a heavy blanket wrapping around you, making outdoor activities feel sticky and uncomfortable for travelers.

September Average Humidity in Mortlake

This chart illustrates the average monthly humidity levels in Mortlake, 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 Mortlake is approximately 82%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec91%89%86%85%79%81%71%76%82%91%92%92%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Mortlake

In Mortlake in September, the maximum UV index is 6, which corresponds to a high Exposure Category. The time to burn is approximately 25 minutes. To find the hourly UV index in Mortlake, you can refer to this Hourly UV Index in Mortlake.

Maximum UV Index Levels in Mortlake for September

The chart shows the monthly maximum UV Index (UVI) for Mortlake 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 Mortlake typically reaches 6, which falls under the high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec124578876421
Data source: Mortlake 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 Mortlake Compares to Other Months

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

This table compares monthly weather conditions in Mortlake, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather5°C (41°F)54 mm (2.1 inches)91%low
February Weather6°C (43°F)53 mm (2.1 inches)89%low
March Weather7°C (46°F)54 mm (2.1 inches)86%moderate
April Weather10°C (49°F)33 mm (1.3 inches)85%moderate
May Weather13°C (55°F)62 mm (2.5 inches)79%high
June Weather16°C (62°F)77 mm (3.0 inches)80%very high
July Weather18°C (65°F)64 mm (2.5 inches)71%very high
August Weather18°C (64°F)70 mm (2.7 inches)76%high
September Weather15°C (59°F)45 mm (1.8 inches)82%high
October Weather12°C (54°F)84 mm (3.3 inches)90%moderate
November Weather8°C (47°F)52 mm (2.0 inches)92%low
December Weather6°C (44°F)84 mm (3.3 inches)92%low

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