September in Adak Island is the sunniest month of the year. In September, the weather in Adak Island is typically warm. Average daily high temperature in September is about 10 degrees above zero. On average, Adak Island has 21 rainy, 6 cloudy, and 3 sunny days in September. The rains are usually heavy. September as well as January, February, March, and April is considered the most uncomfortable time to visit Adak Island.