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September Weather in Brussels, United States

Last updated: June 24, 2025

In September, the average temperature in Brussels, United States is a pleasant 17°C (63°F). Expect the temperature to fluctuate between a cool 5°C (41°F) and a warm 29°C (85°F). During this month, 66 mm (2.6 in) of precipitation is anticipated over approximately 10 days, accompanied by a humidity level averaging around 78%.

September Temperature in Brussels

In September in Brussels, the average temperature is 17°C (63°F). Maximums can reach 29°C (85°F), while minimums can drop as low as 5°C (41°F). This varied climate makes Brussels an ideal destination for travelers looking to experience a mix of warm days and cool evenings.

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

The chart illustrates September temperature patterns in Brussels, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Brussels, September typically has an average temperature of 17°C (63°F), with highs reaching up to 29°C (85°F) and lows dropping to around 5°C (41°F).
JanFebMarAprMayJunJulAugSepOctNovDec222232405264717063513729
Data source: Temperature data for Brussels 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 Brussels

In Brussels in September, the precipitation amount is 66 mm (2.6 in) over the course of 10 days.

September Precipitation Trends in Brussels

The chart displays monthly precipitation patterns in Brussels, 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 Brussels, September typically receives around 66 mm (2.6 inches) of precipitation spread over approximately 10 days.
JanFebMarAprMayJunJulAugSepOctNovDec4250589295101909666995356
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Brussels

In Brussels in September, humidity is 78%. With an average temperature of 17°C (63°F), this humidity feels like a warm, enveloping blanket, making traveling slightly uncomfortable as you navigate the sticky air, prompting the need for frequent breaks in cooler, shaded areas.

September Average Humidity in Brussels

This chart illustrates the average monthly humidity levels in Brussels, 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 Brussels is approximately 78%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec89%90%87%84%77%75%75%73%78%84%89%87%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Brussels

In Brussels in September, the maximum UV index is 7, which corresponds to the high Exposure Category. This means that the time to burn is approximately 25 minutes. For more detailed information, you can check the Hourly UV Index in Brussels.

Maximum UV Index Levels in Brussels for September

The chart shows the monthly maximum UV Index (UVI) for Brussels 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 Brussels typically reaches 7, which falls under the high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec2457910997532
Data source: Brussels 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 Brussels Compares to Other Months

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

This table compares monthly weather conditions in Brussels, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-5°C (23°F)42 mm (1.6 inches)89%low
February Weather-5°C (22°F)50 mm (2.0 inches)90%moderate
March Weather0°C (32°F)58 mm (2.3 inches)87%moderate
April Weather5°C (41°F)92 mm (3.6 inches)84%high
May Weather11°C (53°F)95 mm (3.8 inches)77%very high
June Weather18°C (64°F)101 mm (4.0 inches)75%very high
July Weather22°C (72°F)90 mm (3.6 inches)74%very high
August Weather21°C (70°F)96 mm (3.8 inches)73%very high
September Weather17°C (63°F)66 mm (2.6 inches)78%high
October Weather11°C (51°F)99 mm (3.9 inches)84%moderate
November Weather3°C (37°F)53 mm (2.1 inches)89%moderate
December Weather-2°C (29°F)56 mm (2.2 inches)87%low

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