In May, the weather in Reykyavik is typically cold. Average daily high temperature in May is about 9 degrees above zero. On average, Reykyavik has 16 rainy, 5 sunny, 5 cloudy, and 5 partly cloudy days 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.