August in Rjukan is the rainiest month of the year. In August, the weather in Rjukan is typically warm. Average daily high temperature in August is about 13 degrees above zero. On average, Rjukan has 21 rainy, 4 sunny, 4 cloudy, and 2 partly cloudy days in August. The rains are usually heavy. August as well as April, May, June, and July is considered the most uncomfortable time to visit Rjukan.