August in Perth is the rainiest month of the year. In August, the weather in Perth is typically warm. Average daily high temperature in August is about 16 degrees above zero. On average, Perth has 23 rainy, 4 sunny, 2 cloudy, and 2 partly cloudy days in August. The rains are usually moderate. August as well as January, February, April, and May is considered the most uncomfortable time to visit Perth.