July in Selfoss is the warmest month of the year. In July, the weather in Selfoss is typically warm. Average daily high temperature in July is about 14 degrees above zero. On average, Selfoss has 17 rainy, 7 partly cloudy, 5 sunny, and 2 cloudy days in July. The rains are usually moderate. July as well as January, February, March, and April is considered the most uncomfortable time to visit Selfoss.