Weather in Brussels Brussels has a mild maritime climate and therefore experiences damp, grey and rainy weather. If you are British you know what we are talking about. The coldest months of the year are usually between November and March when temperatures can lower to below freezing, the days are short and there is a lot of rain. There are usually few tourists in Brussels during these months. Summer starts around May and lasts until September, and this is the high tourist season in the city as this is when the weather is best. July and August are the warmest months of the year when temperatures can reach as high as 22C. Be prepared for all seasons in Brussels as the weather is usually unpredictable. Brussels Travel Guide Leave a Reply Cancel Reply Your email address will not be published.CommentName* Email* Website Save my name, email, and website in this browser for the next time I comment.