Rennes has an oceanic climate — mild, wet, and often grey. Summers are pleasant without being hot (average July temperatures around 19°C), and the city never gets the oppressive heat of the south. Rain is possible year-round but falls most heavily from October through January.
The best time to visit is May through September, when café terraces are open and the Jardin du Thabor is at its best. The Saturday market at Place des Lices runs year-round but is especially good in summer when local produce is abundant. The Transmusicales festival in December is one of France's best music events and draws large crowds; hotels book up well in advance.