May in Jasper is the rainiest month of the year. In May, the weather in Jasper is typically cold. Average daily high temperature in May is about 6 degrees above zero. On average, Jasper has 18 rainy, 5 cloudy, 4 sunny, and 4 partly cloudy days in May. The rains are usually moderate. May as well as January, April, June, and October is considered the most uncomfortable time to visit Jasper.