September in Sejdisfjordur is the rainiest month of the year. In September, the weather in Sejdisfjordur is typically cold. Average daily high temperature in September is about 7 degrees above zero. On average, Sejdisfjordur has 25 rainy, 3 sunny, and 2 cloudy days in September. The rains are usually heavy. September as well as January, March, April, and May is considered the most uncomfortable time to visit Sejdisfjordur.