The weather in Rennes is mild most of year, but the lush greenness of Northern France is from the year round rains. Thanks to the northern Gulf Stream there is not much of a variation in the climate in Brittany and the area around Rennes. The town has a generally mild climate, and while it does rain a lot it is never very heavy. On any given day there may be brief, and passing, periods of rain followed by hours of clear, bright skies with high clouds and plenty of sun. All this rain does put a bit of a damp chill in the air however, and visitors seldom have to complain about feeling dry while in Brittany.

The spring and fall are both mild, with cool temperatures but with a few hours of sunlight intermixed with the seasonal rain. This can be a pleasant time to visit, and take in the historic sights. The winter can be a bit gloomier at times during the rain, but even then it seldom reaches below freezing. The winter months from December through March are a bit wetter but there is enough sun once the rains have passed. The winters are mild, with cool but not terribly cold days and cold, but not freezing evenings.

The summers tend to be a bit warmer, and there is a bit more sun. The daytime temperatures can be in the low 70s to the 80s during the day and fall to the low 60s or the high 50s at night. Even in the summer you should be prepared for an occasional cool breeze that could things feel a bit colder, especially at night.