December in Sudbury is the windiest month of the year. In December, the weather in Sudbury is typically cold. Average daily high temperature in December is about 7 degrees above zero. On average, Sudbury has 14 rainy, 11 cloudy, 4 sunny, and 2 partly cloudy days in December. The rains are usually moderate. December as well as January, February, July, and November is considered the most uncomfortable time to visit Sudbury.