May in Penticton is the rainiest month of the year. In May, the weather in Penticton is typically warm. Average daily high temperature in May is about 16 degrees above zero. On average, Penticton has 13 rainy, 8 sunny, 8 partly cloudy, and 2 cloudy days in May. The rains are usually moderate. May as well as February, March, April, and October is considered the most uncomfortable time to visit Penticton.