In September, the weather in Sandnessjoen is typically warm. Average daily high temperature in September is about 11 degrees above zero. On average, Sandnessjoen has 18 rainy, 7 sunny, 3 partly cloudy, and 2 cloudy days in September. The rains are usually heavy. September as well as March, April, May, and June is considered the most uncomfortable time to visit Sandnessjoen.