In August, the weather in Sejdisfjordur is typically cold. Average daily high temperature in August is about 9 degrees above zero. On average, Sejdisfjordur has 23 rainy, 6 cloudy, and 2 sunny days in August. The rains are usually heavy. August as well as January, March, April, and May is considered the most uncomfortable time to visit Sejdisfjordur.