August in Geilo is the rainiest month of the year. In August, the weather in Geilo is typically warm. Average daily high temperature in August is about 10 degrees above zero. On average, Geilo has 19 rainy, 6 cloudy, 3 sunny, and 3 partly cloudy days in August. The rains are usually heavy. August as well as May, June, July, and September is considered the most uncomfortable time to visit Geilo.