December in Riverton is the snowiest and the most freezing month of the year. In December, the weather in Riverton is typically freezing. Average daily high temperature in December is about zero. On average, Riverton has 17 partly cloudy, 13 sunny, and 1 snowy day in December. The snowfalls are usually light. December as well as January, February, March, and November is considered the most uncomfortable time to visit Riverton.