May in Vulcan is the rainiest and the cloudiest month of the year. In May, the weather in Vulcan is typically warm. Average daily high temperature in May is about 16 degrees above zero. On average, Vulcan has 20 rainy, 6 partly cloudy, 4 sunny, and 1 cloudy day in May. The rains are usually heavy. May as well as January, February, March, and April is considered the most uncomfortable time to visit Vulcan.