The most pleasant months of the year for Hat Island are August, July and September. In Hat Island, there are 2 comfortable months with high temperatures in the range of 70-85°. August is the hottest month for Hat Island with an average high temperature of 75.1°, which ranks it as cooler than most places in Washington. December is the snowiest month in Hat Island with 1.6 inches of snow, and 4 months of the year have significant snowfall. There are few days during the summer when the humidity becomes unpleasant.