January in Perth is the sunniest and the coldest month of the year. In January, the weather in Perth is typically cold. Average daily high temperature in January is about 5 degrees above zero. On average, Perth has 12 rainy, 8 cloudy, 7 partly cloudy, and 4 sunny days in January. The rains are usually heavy. January as well as February, March, April, and May is considered the most uncomfortable time to visit Perth.