May in Trier is the rainiest month of the year. In May, the weather in Trier is typically warm. Average daily high temperature in May is about 16 degrees above zero. On average, Trier has 14 rainy, 9 partly cloudy, 5 cloudy, and 3 sunny days in May. The rains are usually moderate. May as well as January, February, March, and April is considered the most uncomfortable time to visit Trier.