August in Sitka is the warmest month of the year. In August, the weather in Sitka is typically warm. Average daily high temperature in August is about 16 degrees above zero. On average, Sitka has 20 rainy, 6 cloudy, 3 sunny, and 2 partly cloudy days in August. The rains are usually heavy. August as well as January, February, March, and April is considered the most uncomfortable time to visit Sitka.