December in Kostanai is the snowiest and the cloudiest month of the year. In December, the weather in Kostanai is typically freezing. Average daily high temperature in December is about 9 degrees below zero. On average, Kostanai has 10 cloudy, 9 partly cloudy, 7 snowy, and 5 sunny days in December. The snowfalls are usually light. December as well as January and February is considered the most uncomfortable time to visit Kostanai.