May in Reykyavik is the sunniest month of the year. In May, the weather in Reykyavik is typically cold. Average daily high temperature in May is about 7 degrees above zero. On average, Reykyavik has 22 rainy, 4 sunny, 4 cloudy, and 1 partly 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 Reykyavik.