December in Selfoss is the coldest month of the year. In December, the weather in Selfoss is typically cold. Average daily high temperature in December is about 1 degree above zero. On average, Selfoss has 20 rainy, 4 sunny, 3 snowy, 2 cloudy, and 2 partly cloudy days in December. The rains are usually heavy. December as well as January, February, March, and April is considered the most uncomfortable time to visit Selfoss.