May in Deadwood is the rainiest month of the year. In May, the weather in Deadwood is typically warm. Average daily high temperature in May is about 15 degrees above zero. On average, Deadwood has 16 rainy, 8 sunny, 6 partly cloudy, and 1 cloudy day in May. The rains are usually heavy. May as well as March and April is considered the most uncomfortable time to visit Deadwood.