September in Santa Susana is the rainiest month of the year. In September, the weather in Santa Susana is typically warm. Average daily high temperature in September is about 23 degrees above zero. On average, Santa Susana has 14 rainy, 8 sunny, 6 partly cloudy, and 2 cloudy days in September. The rains are usually heavy. September as well as January, February, March, and April is considered the most uncomfortable time to visit Santa Susana.