September in Anchorage is the rainiest month of the year. In September, the weather in Anchorage is typically warm. Average daily high temperature in September is about 11 degrees above zero. On average, Anchorage has 18 rainy, 6 sunny, 5 partly cloudy, and 1 cloudy day in September. The rains are usually moderate. September as well as April, July, August, and October is considered the most uncomfortable time to visit Anchorage.