Bremen has a cool, maritime climate — mild but overcast for much of the year, with rain possible in any month. An umbrella is always sensible. The best months for visiting are May, June, and September, when temperatures are comfortable (15-22 degrees C), the days are long, and the city is lively without the peak summer crowds.
July and August are the busiest months for domestic tourism. The Schlachte waterfront and outdoor spaces are at their best in summer. Winter is grey and cold but not harsh, and the Christmas market on the Marktplatz and along the Schlachte embankment is one of the better in northern Germany.
The Freimarkt fair in October, one of Germany's oldest folk festivals (dating to 1035), brings a fairground, beer tents, and considerable noise to the Burgerweide for two weeks.