In September, the weather in Bolshiye Siby is typically warm. Average daily high temperature in September is about 14 degrees above zero. On average, Bolshiye Siby has 15 rainy, 12 cloudy, and 3 sunny days in September. The rains are usually moderate. September as well as January, February, April, and October is considered the most uncomfortable time to visit Bolshiye Siby.