December in Nyköping is the rainiest and the windiest month of the year. In December, the weather in Nyköping is typically cold. Average daily high temperature in December is about 2 degrees above zero. On average, Nyköping has 17 rainy, 8 cloudy, 3 sunny, 2 partly cloudy, and 1 snowy day in December. The rains are usually moderate. December as well as November is considered the most uncomfortable time to visit Nyköping.