January in Dortmund is the coldest month of the year. In January, the weather in Dortmund is typically cold. Average daily high temperature in January is about 3 degrees above zero. On average, Dortmund has 20 rainy, 7 cloudy, 3 sunny, and 1 partly cloudy day in January. The rains are usually heavy. January as well as February, March, October, and November is considered the most uncomfortable time to visit Dortmund.