December in Ulm is the cloudiest month of the year. In December, the weather in Ulm is typically cold. Average daily high temperature in December is about 2 degrees above zero. On average, Ulm has 10 cloudy, 10 partly cloudy, 7 rainy, 2 snowy, and 2 sunny days in December. The rains are usually heavy. December as well as January, February, March, and April is considered the most uncomfortable time to visit Ulm.