May in Derby is the rainiest month of the year. In May, the weather in Derby is typically warm. Average daily high temperature in May is about 25 degrees above zero. On average, Derby has 13 sunny, 12 rainy, 4 partly cloudy, and 2 cloudy days in May. The rains are usually heavy. May as well as January, February, June, and July is considered the most uncomfortable time to visit Derby.