May in Pittsburg is the rainiest and the cloudiest month of the year. In May, the weather in Pittsburg is typically warm. Average daily high temperature in May is about 25 degrees above zero. On average, Pittsburg has 13 rainy, 10 sunny, 6 partly cloudy, and 2 cloudy days in May. The rains are usually heavy. May as well as January, February, March, and June is considered the most uncomfortable time to visit Pittsburg.