December in Richland is the coldest month of the year. In December, the weather in Richland is typically cold. Average daily high temperature in December is about 1 degree above zero. On average, Richland has 15 cloudy, 8 rainy, 3 snowy, 3 sunny, and 2 partly cloudy days in December. The rains are usually light. December as well as January, February, March, and November is considered the most uncomfortable time to visit Richland.