May in Brno is the rainiest month of the year. In May, the weather in Brno is typically warm. Average daily high temperature in May is about 17 degrees above zero. On average, Brno has 15 rainy, 10 sunny, 5 partly cloudy, and 1 cloudy day in May. The rains are usually moderate. May as well as January, February, March, and November is considered the most uncomfortable time to visit Brno.