May in Lethbridge is the rainiest month of the year. In May, the weather in Lethbridge is typically warm. Average daily high temperature in May is about 16 degrees above zero. On average, Lethbridge has 12 rainy, 9 partly cloudy, 7 sunny, and 3 cloudy days in May. The rains are usually moderate. May as well as February, March, April, and November is considered the most uncomfortable time to visit Lethbridge.