In September, the weather in Bol'shaya Kosul' is typically warm. Average daily high temperature in September is about 11 degrees above zero. On average, Bol'shaya Kosul' has 16 rainy, 6 partly cloudy, 5 sunny, and 3 cloudy days in September. The rains are usually moderate. September as well as January, February, April, and May is considered the most uncomfortable time to visit Bol'shaya Kosul'.