April in Mainz is the sunniest month of the year. In April, the weather in Mainz is typically warm. Average daily high temperature in April is about 13 degrees above zero. On average, Mainz has 12 rainy, 9 sunny, 8 partly cloudy, and 1 cloudy day in April. The rains are usually moderate. April as well as January, February, March, and October is considered the most uncomfortable time to visit Mainz.