January in Mannheim is the coldest month of the year. In January, the weather in Mannheim is typically cold. Average daily high temperature in January is about 3 degrees above zero. On average, Mannheim has 15 rainy, 11 cloudy, 4 sunny, and 1 partly cloudy day in January. The rains are usually light. January as well as February, November, and December is considered the most uncomfortable time to visit Mannheim.