August in Bethel Park is the sunniest month of the year. In August, the weather in Bethel Park is typically warm. Average daily high temperature in August is about 26 degrees above zero. On average, Bethel Park has 16 sunny, 9 partly cloudy, and 6 rainy days in August. The rains are usually moderate. August as well as September is considered the most comfortable time to visit Bethel Park.