April in Ulm is the sunniest month of the year. In April, the weather in Ulm is typically warm. Average daily high temperature in April is about 13 degrees above zero. On average, Ulm has 12 rainy, 8 sunny, 7 partly cloudy, and 3 cloudy days in April. The rains are usually heavy. April as well as January, February, March, and May is considered the most uncomfortable time to visit Ulm.