In September, the weather in Sosnovoborsk is typically warm. Average daily high temperature in September is about 12 degrees above zero. On average, Sosnovoborsk has 13 rainy, 6 sunny, 6 partly cloudy, and 5 cloudy days in September. The rains are usually light. September as well as January, February, April, and May is considered the most uncomfortable time to visit Sosnovoborsk.