August in Yamaguchi is the warmest month of the year. In August, the weather in Yamaguchi is typically warm. Average daily high temperature in August is about 27 degrees above zero. On average, Yamaguchi has 22 rainy, 8 sunny, and 1 partly cloudy day in August. The rains are usually heavy. August as well as January, February, March, and June is considered the most uncomfortable time to visit Yamaguchi.