May in Rock Hill is the rainiest month of the year. In May, the weather in Rock Hill is typically warm. Average daily high temperature in May is about 25 degrees above zero. On average, Rock Hill has 13 rainy, 11 sunny, 5 partly cloudy, and 2 cloudy days in May. The rains are usually heavy. May as well as January, February, and December is considered the most uncomfortable time to visit Rock Hill.