December in Oshkosh is the snowiest and the windiest month of the year. In December, the weather in Oshkosh is typically freezing. Average daily high temperature in December is about 3 degrees below zero. On average, Oshkosh has 17 cloudy, 9 snowy, 3 sunny, 1 rainy, and 1 partly cloudy day in December. The snowfalls are usually light.