May in Thurso is the sunniest month of the year. In May, the weather in Thurso is typically warm. Average daily high temperature in May is about 10 degrees above zero. On average, Thurso has 20 rainy, 6 sunny, 4 cloudy, and 1 partly cloudy day in May. The rains are usually moderate. May as well as January, February, March, and April is considered the most uncomfortable time to visit Thurso.