December in Koblenz is the rainiest and the windiest month of the year. In December, the weather in Koblenz is typically cold. Average daily high temperature in December is about 4 degrees above zero. On average, Koblenz has 17 rainy, 11 cloudy, 2 sunny, and 1 partly cloudy day in December. The rains are usually moderate. December as well as January, February, and November is considered the most uncomfortable time to visit Koblenz.