December in Sejdisfjordur is the snowiest, the windiest, and the most freezing month of the year. In December, the weather in Sejdisfjordur is typically freezing. Average daily high temperature in December is about zero. On average, Sejdisfjordur has 22 snowy, 4 rainy, 3 cloudy, and 2 sunny days in December. The snowfalls are usually heavy.