December in Ilmenau is the rainiest, the windiest, and the cloudiest month of the year. In December, the weather in Ilmenau is typically cold. Average daily high temperature in December is about 2 degrees above zero. On average, Ilmenau has 21 rainy, 7 cloudy, 2 sunny, and 1 snowy day in December. The rains are usually moderate. December as well as February, March, and November is considered the most uncomfortable time to visit Ilmenau.