May in Zermatt is the rainiest and the cloudiest month of the year. In May, the weather in Zermatt is typically cold. Average daily high temperature in May is about 5 degrees above zero. On average, Zermatt has 30 rainy and 1 sunny day in May. The rains are usually heavy. May as well as April, June, July, and August is considered the most uncomfortable time to visit Zermatt.