August in Chilliwack is the warmest month of the year. In August, the weather in Chilliwack is typically warm. Average daily high temperature in August is about 19 degrees above zero. On average, Chilliwack has 15 sunny, 8 partly cloudy, 6 rainy, and 2 cloudy days in August. The rains are usually light. August as well as July is considered the most comfortable time to visit Chilliwack.