May in Canonsburg is the rainiest month of the year. In May, the weather in Canonsburg is typically warm. Average daily high temperature in May is about 21 degrees above zero. On average, Canonsburg has 21 rainy, 7 sunny, 2 cloudy, and 1 partly 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 Canonsburg.