May in Stornoway is the sunniest month of the year. In May, the weather in Stornoway is typically warm. Average daily high temperature in May is about 11 degrees above zero. On average, Stornoway has 20 rainy, 7 sunny, 2 cloudy, and 2 partly cloudy days in May. The rains are usually moderate. May as well as January, February, March, and April is considered the most uncomfortable time to visit Stornoway.