August in Wailuku is the sunniest month of the year. In August, the weather in Wailuku is typically warm. Average daily high temperature in August is about 25 degrees above zero. On average, Wailuku has 23 sunny, 6 partly cloudy, 1 rainy, and 1 cloudy day in August. The rains are usually light. August as well as January, May, June, and July is considered the most comfortable time to visit Wailuku.