Climate averages 1991–2020
Brussels weather
in September.
A mild, moderately wet month: the 4th warmest and the 2nd driest of the year.
Long-term climate patterns, not a forecast for a particular trip.
September is a mild month in Brussels: daytime highs average 19.2°C and nights cool to about 11.7°C. By daytime temperature it is the 4th warmest of the 12 months.
Expect about 54 mm of rain on roughly 11 days, which makes September a moderately wet month (the 2nd driest of the 12 months). Daylight, from sunrise to sunset, lasts about 12 h 41 min on an average September day.
The nearest other city in this atlas is Ixelles (2 km away). In September its highs average 18.9°C, about as warm as Brussels, with 54 mm of rain.
Among the 18 cities listed in Belgium, Brussels ranks joint 3rd of 18 for the warmest September highs and joint 4th of 18 for the driest September (rainfall, lowest first). The mean September high of those 18 cities is 19.0°C; Brussels is 0.2°C warmer than that mean.
From September to October, average highs fall by 4.3°C to 14.9°C, and monthly rainfall rises from 54 mm to 58 mm.
The annual picture
September in context
Monthly rainfall
Average total · mmAverages from hourly ERA5 reanalysis data. Actual weather varies from year to year. How these numbers are calculated
Every month, side by side
Brussels climate table
| Month | Average highHigh / low | Average low | Rainfall mm/month | Rain days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 6.1°C1.4°C | 1.4°C | 63 | 12.0 | 8.58 h |
| February | 7.2°C1.4°C | 1.4°C | 58 | 11.4 | 10.010 h |
| March | 10.6°C3.1°C | 3.1°C | 56 | 11.8 | 11.812 h |
| April | 14.4°C5.4°C | 5.4°C | 48 | 11.4 | 13.814 h |
| May | 17.8°C9.1°C | 9.1°C | 62 | 12.2 | 15.515 h |
| June | 20.6°C12.1°C | 12.1°C | 65 | 11.5 | 16.416 h |
| July | 22.6°C14.3°C | 14.3°C | 70 | 12.2 | 16.016 h |
| August | 22.5°C14.2°C | 14.2°C | 73 | 12.1 | 14.615 h |
| September, selected | 19.2°C11.7°C | 11.7°C | 54 | 10.5 | 12.713 h |
| October | 14.9°C8.7°C | 8.7°C | 58 | 11.2 | 10.811 h |
| November | 9.9°C5.0°C | 5.0°C | 64 | 11.9 | 9.09 h |
| December | 6.6°C2.2°C | 2.2°C | 74 | 13.0 | 8.08 h |
Rainfall is the average of the 30 separate monthly totals. A rain day is a local calendar day with at least 1 mm of precipitation. Daylight is the calculated sunrise-to-sunset length, not measured sunshine.
Compare places
September in nearby cities
- Ixelles in SeptemberBelgium · 2 kmHigh 18.9°C · Low 11.4°C · 54 mm rain
- Anderlecht in SeptemberBelgium · 3 kmHigh 19.3°C · Low 11.8°C · 54 mm rain
- Schaerbeek in SeptemberBelgium · 3 kmHigh 19.2°C · Low 11.7°C · 56 mm rain
- Mechelen in SeptemberBelgium · 21 kmHigh 19.3°C · Low 11.8°C · 52 mm rain
- Aalst in SeptemberBelgium · 24 kmHigh 19.2°C · Low 11.9°C · 55 mm rain
- Leuven in SeptemberBelgium · 25 kmHigh 19.2°C · Low 11.7°C · 53 mm rain
- Antwerp in SeptemberBelgium · 41 kmHigh 19.0°C · Low 12.0°C · 57 mm rain
- La Louvière in SeptemberBelgium · 42 kmHigh 18.7°C · Low 11.1°C · 54 mm rain
Read the numbers correctly
Climate, not a promise.
These patterns help compare months. They cannot tell you the weather on a specific day of your trip.
Sources, method and limitsHow these numbers are made (what the highs, lows and rain days mean, the sources and the model cell used for Brussels) is explained once on the Brussels year overview and on the Sources, method and limits page.
Anderlecht and Ixelles lie in the same rainfall cell, so their rainfall figures are identical to these; temperatures differ because they come from smaller 0.1° cells.