January in Yamaguchi is the windiest, the cloudiest, and the coldest month of the year. In January, the weather in Yamaguchi is typically cold. Average daily high temperature in January is about 9 degrees above zero. On average, Yamaguchi has 12 partly cloudy, 11 rainy, 5 cloudy, and 3 sunny days in January. The rains are usually moderate. January as well as February, March, July, and August is considered the most uncomfortable time to visit Yamaguchi.