August in Duluth is the sunniest month of the year. In August, the weather in Duluth is typically warm. Average daily high temperature in August is about 23 degrees above zero. On average, Duluth has 18 sunny, 10 partly cloudy, 2 rainy, and 1 cloudy day in August. The rains are usually heavy. August as well as {{month_nom: February}}, and {{month_nom: February}} is considered the most comfortable time to visit Duluth.