In September, Brussels typically sees daytime highs of 19.4°C and overnight lows around 10.1°C. Compared to the annual average high of 13.8°C, September runs +5.6°C.
September in Brussels averages a daytime high of 19.4°C and an overnight low of 10.1°C.
September runs +5.6°C compared to Brussels's annual average high of 13.8°C, ranking #4 of 12 months by warmth.
Plan for daytime highs near 19.4°C and cooler evenings around 10.1°C.