In December, the weather in Kostromskaya is typically cold. Average daily high temperature in December is about 6 degrees above zero. On average, Kostromskaya has 10 sunny, 10 partly cloudy, 7 rainy, and 4 cloudy days in December. The rains are usually light. December as well as January, February, March, and May is considered the most uncomfortable time to visit Kostromskaya.