September Weather in Brussels, Belgium

Last updated: August 21, 2025

September in Brussels, Belgium offers a delightful blend of seasonal transitions, showcasing a maximum temperature peaking at 33°C (91°F), while the average, a more moderate 15°C (60°F), provides comfort for outdoor activities. Early mornings can be brisk, with temperatures dipping to a minimum of 4°C (39°F). This month is characteristic of increased humidity at 82%, contributing to a soft, atmospheric feel. Visitors can expect some rain, with precipitation amounting to 55 mm (2.2 in) over 9 rainy days, ideal for those who appreciate a refreshing autumn climate. Embrace the rich culture of Brussels as you navigate its charming streets amidst this vibrant weather!

September Temperature in Brussels

As summer fades into autumn, September in Brussels showcases a delightful transition in temperatures. With minimums around 4°C (39°F) and average highs peaking at 33°C (91°F), this month offers a refreshing climate for exploration. The average temperature settles at 15°C (60°F), making it a sweet spot for enjoying the city's vibrant outdoor scenes. While it marks the tail end of the warmer months, September's warmth is a gentle reminder of summer's lingering embrace, inviting residents and visitors alike to take advantage of the pleasant weather before the cooler October sets in.

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 {2}°C ({3}°F), with highs reaching up to {4}°C ({5}°F) and lows dropping to around {6}°C ({7}°F).
JanFebMarAprMayJunJulAugSepOctNovDec394245505664666660544542
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

As autumn approaches, September in Brussels often sees a notable shift in precipitation patterns. With an average of 55 mm (2.2 in) of rain spread over 9 days, this month marks a decline from the wetter summer months, notably August, which recorded 80 mm (3.2 in) of rainfall. Despite the reduced precipitation, September's weather can still be quite unpredictable, making for a refreshing yet sometimes dreary start to the fall season. As the days grow shorter, the gentle drizzles and occasional downpours contribute to the lush greenery that the city is known for, balancing the influences of the summer's warmth with the impending chill of autumn.

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 {2} mm ({3} inches) of precipitation spread over approximately {4} days.
JanFebMarAprMayJunJulAugSepOctNovDec656971375866718055765793
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Brussels

In September, Brussels experiences a noticeable shift in humidity, with levels hovering around 82%. This slight rise from the drier August, which saw humidity at 76%, signals the onset of autumn as the air retains more moisture. It’s interesting to observe how the humidity gradually increases from summer’s lows, peaking in the colder months of November and December at 92%. Overall, September stands out as a transitional month, balancing the fading warmth of summer with the crispness of fall, making it a unique time for both locals and visitors to enjoy the city’s charm before winter sets in.

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 {2}%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec91%89%87%85%82%82%80%76%82%89%92%92%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Brussels

As September unfolds in Brussels, the UV Index settles at a moderate 5, making it essential to be mindful of sun exposure, particularly during peak hours. This marks a slight decline from the summer months, where the index frequently soared to 8, but still necessitates caution with a burn time of 30 minutes. As the vibrant greenery of autumn begins to take over, sunlight remains warm, allowing for outdoor enjoyment without the intense UV risks of July and June. Observing how the UV Index decreased from the summer's high values to September's moderate level suggests a seasonal transition, where sun-seekers should balance fun in the sun with skin protection. For comprehensive insights on UV levels throughout the year, check the Brussels UV Index.

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 {2}, which falls under the {3} exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec124578875421
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.

September Sunshine in Brussels

September in Brussels shines with an impressive 319 hours of sunshine, marking a transition from the summer's peak into the cooler months. This month enjoys a substantial decline from July's high of 406 hours, yet it holds onto a favorable glow as it outshines October's 240 hours significantly. The trend reflects a typical pattern in Brussels, where the sun graces the city generously from March through August, culminating in a vibrant summer. As autumn sets in, September's ample sunlight provides a golden farewell to the warmth, making it a prime time for enjoying the city's beautiful parks and outdoor cafés. The progressive drop in sunshine hours hints at the approaching winter, but September stands a bright highlight in the yearly cycle.

Monthly Sunshine Duration in Brussels: September Highlighted

The September sunshine duration represents the total number of hours Brussels experiences direct sunlight during the month of September, excluding cloudy or obstructed periods. This chart compares the sunshine duration of September with the other months of the year.
JanFebMarAprMayJunJulAugSepOctNovDec121h200h266h346h394h398h406h379h319h240h190h143h
Data source: Brussels September Sunshine duration data generated using information from the Copernicus Climate Change Service.

Chance of Sun in Brussels During September

In September, Brussels experiences a 36% chance of sunny weather, marking a slight improvement as summer transitions into autumn. This is a notable increase compared to the earlier months of July and August, which hover around 34% and 29% respectively. As the city bids farewell to the warmest season, the likelihood of sunshine begins to stabilize, moving closer to the more promising conditions seen in spring, particularly April with its 50% chance. While September weather can be unpredictable, it offers a refreshing blend of sun and the emerging hues of autumn, making it a delightful time to explore the city's rich culture and vibrant landscapes.

Percentage of Sunny Days in September in Brussels

The chart illustrates the percentage of sunny days in Brussels throughout the year, with September highlighted. It highlights the variation in sunshine across each month and provides an overview of the typical frequency of sunny days, offering insights into how often Brussels experiences clear skies throughout the year.
JanFebMarAprMayJunJulAugSepOctNovDec11%30%40%50%33%34%34%29%36%32%24%16%
Data source: Brussels September chance of sun data, generated using information from the Copernicus Climate Change Service.

Daylight Hours in Brussels in September

In September, Brussels transitions from the height of summer into the crisp beginnings of autumn, with daylight lasting approximately 12 hours. This marks a notable decrease from the long, sun-drenched days of June and July, where residents enjoyed 16 and 15 hours of light, respectively. As the city embraces the changing seasons, daylight gradually wanes, which can be seen as a precursor to the shorter hours of October and the darker winter months that follow. The shift in daylight serves as a gentle reminder of the natural cycles, encouraging both locals and visitors to savor the lingering warmth of early fall before the days shorten significantly.

Average Daylight Hours in Brussels for September

The chart illustrates the variation in daylight duration in Brussels throughout the year, with September highlighted. It shows the monthly changes in daylight hours, calculated by summing the hours between sunrise and sunset.
JanFebMarAprMayJunJulAugSepOctNovDec8h 31m10h 2m11h 55m13h 50m15h 31m16h 23m15h 55m14h 25m12h 34m10h 39m8h 56m8h 2m
Data source: Brussels daylight hours, calculated by summing the hours between sunrise and sunset for each day.

September Winds in Brussels

As September unfolds in Brussels, the winds gently whisper at an average speed of 3.0 m/s (7 mph), marking a subtle shift in the breezy rhythm of the city. This is a notable decline from the more blustery months of May and January, which often see higher gusts around 4.4 m/s (10 mph). The month of September transitions smoothly from the summer's calmer June and July winds of 2.8 m/s and 3.3 m/s, hinting at the onset of autumn. As the leaves begin to turn, the softer winds create a serene atmosphere, inviting residents and visitors alike to enjoy leisurely strolls through the streets of this vibrant capital. In the grand scheme, September's mild breezes not only reflect the seasonal changes but also signal a gentle preparation for the winds of October, which will pick up once again to an average of 4.3 m/s (10 mph).

Average September Wind Speed in Brussels

The chart displays monthly wind speed patterns in Brussels, with values for each month shown alongside September's data, which is highlighted for easy comparison. It illustrates the average wind speed, offering insights into how September's wind conditions compare to the rest of the year.
JanFebMarAprMayJunJulAugSepOctNovDec4.44.64.03.44.42.83.33.43.0 m/s4.33.34.2
Data source: Brussels September wind data, generated using information from the Copernicus Climate Change Service.

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.

September and January present contrasting weather conditions. In September, temperatures are generally milder, with a minimum of 4°C (39°F), an average of 15°C (60°F), and a maximum reaching 33°C (91°F). The humidity is relatively high at 82%, and the month experiences about 55 mm (2.2 in) of precipitation over approximately 9 days. In contrast, January brings much colder weather, with temperatures ranging from a minimum of -7°C (20°F) to a maximum of 14°C (57°F) and an average of just 4°C (39°F). Precipitation slightly increases to 65 mm (2.5 in) over about 12 days, and humidity peaks at 91%. For more details on January conditions, visit Brussels weather in January.

September and February showcase striking contrasts in weather. In September, temperatures range from a mild 4°C (39°F) to a warm 33°C (91°F), averaging around 15°C (60°F), while February experiences a chillier climate with temperatures dipping as low as -8°C (17°F), peaking at a maximum of 19°C (66°F) and averaging just 5°C (42°F). Additionally, February tends to be wetter, with 69 mm (2.7 in) of precipitation over 12 days, compared to September's 55 mm (2.2 in) over 9 days. The humidity is also higher in February at 89% versus September's 82%. For more detailed insights, check out Brussels weather in February.

In September, the weather showcases a significant warmth, with temperatures ranging from a chilly 4°C (39°F) to a maximum of 33°C (91°F), making it an ideal time for outdoor activities. The average temperature sits at a comfortable 15°C (60°F), with fairly moderate precipitation at 55 mm over 9 days and humidity around 82%. In contrast, March brings a much cooler climate, with temperatures dipping as low as -8°C (17°F) and averaging just 7°C (45°F). While it can peak at 23°C (74°F), it experiences higher precipitation at 70 mm over 14 days, along with increased humidity at 87%. For more specific details on weather conditions in March, you can check Brussels weather in March.

In comparing the weather of September and April, there are notable contrasts in temperature and precipitation. September typically enjoys warmer temperatures with a range from a chilly 4°C (39°F) at night to a high of 33°C (91°F) during the day, averaging about 15°C (60°F). In contrast, April experiences cooler temperatures, with a minimum of -4°C (26°F) and a maximum of 27°C (80°F), culminating in an average of 10°C (50°F). Precipitation is slightly more pronounced in September, totaling 55 mm (2.2 in) across approximately 9 days, compared to April's 37 mm (1.5 in) over just 8 days. Humidity levels are also relatively high in both months, with September at 82% and April slightly higher at 85%. For those looking to understand April weather specifically, more details can be found at Brussels weather in April.

When comparing the weather in September and May, both months exhibit mild conditions with relatively high humidity levels at 82%. September tends to be warmer, with average temperatures reaching 15°C (60°F) and a maximum of 33°C (91°F), while May shows slightly cooler conditions, averaging 13°C (57°F) and peaking at 31°C (88°F). Precipitation is fairly similar, with September receiving 55 mm (2.2 in) over 9 days, compared to May's 58 mm (2.3 in) across 12 days. For more detailed information on May weather, you can check this link: Brussels weather in May.

In September, the weather presents a slightly cooler profile compared to June, with minimum temperatures dipping to 4°C (39°F) and an average of 15°C (60°F). The peak temperature can reach a warm 33°C (91°F), but overall, the days feel milder as summer transitions into autumn. Precipitation in September averages 55 mm (2.2 in) over 9 days, maintaining a humidity level of 82%.

Conversely, June experiences slightly warmer minimum temperatures starting at 7°C (44°F) and an average of 18°C (65°F), with a maximum temperature similar to September at 32°C (91°F). Rainfall is a bit higher at 66 mm (2.6 in), also spread over 9 days, yet it shares the same humidity level of 82%. For a detailed look at the weather conditions, visit Brussels weather in June.

In comparing the weather between September and July, September tends to have cooler temperatures, with a minimum of 4°C (39°F) and an average of 15°C (60°F), while July experiences a warmer minimum of 8°C (46°F) and an average of 19°C (66°F). The maximum temperatures in July can reach up to 39°C (102°F), significantly higher than the 33°C (91°F) observed in September. Precipitation is slightly lower in September at 55 mm (2.2 in) over 9 days, compared to July's 71 mm (2.8 in) over 11 days. Additionally, humidity levels are quite similar, with September at 82% and July at 80%. For more details, you can check out Brussels weather in July.

In comparing the weather of September and August, it's clear that September experiences a broader temperature range, with minimums dropping to 4°C (39°F) and maximums reaching up to 33°C (91°F), while August maintains a milder range with minimums at 8°C (46°F) and maximums peaking at 36°C (97°F). Precipitation is also more frequent in August, with rain falling on 14 days and totaling 80 mm (3.2 in), compared to September’s 55 mm (2.2 in) over 9 days. Humidity levels are slightly higher in September at 82%, compared to 76% in August, which can make the transitioning warmth feel quite muggy. For more detailed insights into August weather, check out Brussels weather in August.

September and October exhibit notable differences in weather patterns. September tends to be warmer, with temperatures ranging from a minimum of 4°C (39°F) to a maximum of 33°C (91°F) and an average of 15°C (60°F). In contrast, October sees cooler temperatures, peaking at 25°C (77°F) and averaging 12°C (54°F), with a minimum of just 1°C (34°F). Precipitation also increases in October, with 76 mm (3.0 in) over 13 days compared to September's 55 mm (2.2 in) over 9 days. Additionally, humidity rises from 82% in September to 89% in October, contributing to a distinctly more brisk and damp feel. For more detailed weather insights, you can check Brussels weather in October.

In comparing the weather of September and November, we can see a significant transition as summer gives way to autumn. September features milder temperatures, with a minimum of 4°C (39°F) and an average of 15°C (60°F), peaking at a warm 33°C (91°F). The month experiences about 55 mm (2.2 in) of precipitation over approximately 9 days, along with relatively high humidity at 82%.

In contrast, November brings a notable dip in temperature, with minimums reaching -2°C (28°F) and an average of 7°C (45°F). Daytime highs are much cooler, maxing out at 18°C (65°F). Precipitation slightly increases to 57 mm (2.2 in) over 11 days, and humidity rises to 92%, contributing to an overall chillier atmosphere. For more detailed insights on the weather conditions, you can refer to Brussels weather in November.

In September, temperatures range significantly, with a minimum of 4°C (39°F) and a maximum of 33°C (91°F), resulting in an average of 15°C (60°F). The month experiences 55 mm (2.2 in) of precipitation over about 9 days, and the humidity sits at a comfortable 82%. In contrast, December brings much colder conditions, with temperatures dropping to a minimum of -5°C (24°F) and an average of just 5°C (42°F), peaking at 15°C (59°F). Precipitation increases to 93 mm (3.7 in) across 17 days, and humidity rises slightly to 92%. For more details on what to expect during this chilly month, visit Brussels weather in December.

Compare Brussels's Climate with Cities Worldwide

Conclusion: What to Expect From September Weather in Brussels

As September unfolds in Brussels, the weather presents a delightful transition from the warmth of summer to the crispness of autumn. With temperatures peaking at a toasty 33°C and settling around a mild 15°C, this month stands out as a time of comfortable warmth before winter sets in. Visitors may experience the occasional rainfall, with about nine days of precipitation adding to the city's charm, while humidity levels hover around 82%. This unique climate makes September a great time for explorations, as the bustling city offers a mix of pleasant days and cooler nights. To learn more about what to expect throughout the year, visit Brussels Climate.