In August, the weather in Sejdisfjordur is typically warm. Average daily high temperature in August is about 12 degrees above zero. On average, Sejdisfjordur has 14 rainy, 8 cloudy, 7 partly cloudy, and 2 sunny days in August. The rains are usually moderate. August as well as April, May, June, and July is considered the most uncomfortable time to visit Sejdisfjordur.