May in Jacksonville is the rainiest month of the year. In May, the weather in Jacksonville is typically hot. Average daily high temperature in May is about 29 degrees above zero. On average, Jacksonville has 12 rainy, 10 sunny, 7 partly cloudy, and 2 cloudy days in May. The rains are usually heavy. May as well as June, July, August, and December is considered the most uncomfortable time to visit Jacksonville.