May in Cannes is the rainiest month of the year. In May, the weather in Cannes is typically warm. Average daily high temperature in May is about 19 degrees above zero. On average, Cannes has 14 rainy, 10 sunny, 6 partly cloudy, and 1 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 Cannes.