December in Leavenworth is the snowiest and the most freezing month of the year. In December, the weather in Leavenworth is typically freezing. Average daily high temperature in December is about 1 degree below zero. On average, Leavenworth has 12 cloudy, 10 snowy, 5 partly cloudy, 3 sunny, and 1 rainy day in December. The snowfalls are usually heavy. December as well as January, February, March, and April is considered the most uncomfortable time to visit Leavenworth.