May in Kostomucsha is the sunniest month of the year. In May, the weather in Kostomucsha is typically warm. Average daily high temperature in May is about 10 degrees above zero. On average, Kostomucsha has 16 rainy, 6 sunny, 6 partly cloudy, and 3 cloudy days in May. The rains are usually moderate. May as well as January, April, June, and August is considered the most uncomfortable time to visit Kostomucsha.