May in Green River is the rainiest month of the year. In May, the weather in Green River is typically warm. Average daily high temperature in May is about 15 degrees above zero. On average, Green River has 11 rainy, 10 partly cloudy, 8 sunny, and 2 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 Green River.