December in Olsztyn is the windiest month of the year. In December, the weather in Olsztyn is typically cold. Average daily high temperature in December is about 1 degree above zero. On average, Olsztyn has 12 cloudy, 10 rainy, 4 snowy, 3 partly cloudy, and 2 sunny days in December. The rains are usually moderate. December as well as March and November is considered the most uncomfortable time to visit Olsztyn.