December in Rennes is the windiest month of the year. In December, the weather in Rennes is typically cold. Average daily high temperature in December is about 8 degrees above zero. On average, Rennes has 16 rainy, 5 sunny, 5 cloudy, and 5 partly cloudy days in December. The rains are usually moderate. December as well as January, February, May, and November is considered the most uncomfortable time to visit Rennes.