May in Celje is the rainiest month of the year. In May, the weather in Celje is typically warm. Average daily high temperature in May is about 17 degrees above zero. On average, Celje has 18 rainy, 9 sunny, and 4 partly cloudy days in May. The rains are usually heavy. May as well as February, March, April, and November is considered the most uncomfortable time to visit Celje.