April in Flensburg is the sunniest month of the year. In April, the weather in Flensburg is typically warm. Average daily high temperature in April is about 11 degrees above zero. On average, Flensburg has 11 rainy, 9 sunny, 8 partly cloudy, and 2 cloudy days in April. The rains are usually moderate. April as well as January, February, March, and October is considered the most uncomfortable time to visit Flensburg.