December in Boise is the snowiest month of the year. In December, the weather in Boise is typically freezing. Average daily high temperature in December is about 1 degree above zero. On average, Boise has 8 snowy, 7 sunny, 7 cloudy, 5 rainy, and 4 partly cloudy days in December. The snowfalls are usually moderate. December as well as January, February, March, and November is considered the most uncomfortable time to visit Boise.