August in Matsuyama is the hottest month of the year. In August, the weather in Matsuyama is typically hot. Average daily high temperature in August is about 28 degrees above zero. On average, Matsuyama has 17 rainy, 8 sunny, 4 partly cloudy, and 2 cloudy days in August. The rains are usually heavy. August as well as January, February, July, and December is considered the most uncomfortable time to visit Matsuyama.