May in Rio Mayo is the cloudiest month of the year. In May, the weather in Rio Mayo is typically cold. Average daily high temperature in May is about 9 degrees above zero. On average, Rio Mayo has 16 partly cloudy, 9 sunny, 5 cloudy, and 1 rainy day in May. The rains are usually light. May as well as June, July, August, and September is considered the most uncomfortable time to visit Rio Mayo.