September in Stellenbosch is the cloudiest month of the year. In September, the weather in Stellenbosch is typically warm. Average daily high temperature in September is about 16 degrees above zero. On average, Stellenbosch has 12 sunny, 10 partly cloudy, and 8 rainy days in September. The rains are usually moderate. September as well as June and August is considered the most uncomfortable time to visit Stellenbosch.