August in St. George is the warmest month of the year. In August, the weather in St. George is typically hot. Average daily high temperature in August is about 28 degrees above zero. On average, St. George has 16 rainy, 13 sunny, and 2 partly cloudy days in August. The rains are usually heavy. August as well as January, February, and September is considered the most uncomfortable time to visit St. George.