December in Washington is the coldest month of the year. In December, the weather in Washington is typically cold. Average daily high temperature in December is about 4 degrees above zero. On average, Washington has 10 rainy, 10 sunny, 10 partly cloudy, and 1 cloudy day in December. The rains are usually heavy. December as well as January, February, March, and April is considered the most uncomfortable time to visit Washington.