December in Brussels is the windiest month of the year. In December, the weather in Brussels is typically cold. Average daily high temperature in December is about 6 degrees above zero. On average, Brussels has 13 rainy, 13 cloudy, 3 sunny, and 2 partly cloudy days in December. The rains are usually moderate. December as well as January, February, October, and November is considered the most uncomfortable time to visit Brussels.