September in The Valley is the hottest month of the year. In September, the weather in The Valley is typically hot. Average daily high temperature in September is about 29 degrees above zero. On average, The Valley has 13 rainy, 12 sunny, 4 partly cloudy, and 1 cloudy day in September. The rains are usually light. September as well as August, October, and November is considered the most uncomfortable time to visit The Valley.