In September, the weather in Bronnoysund is typically warm. Average daily high temperature in September is about 12 degrees above zero. On average, Bronnoysund has 19 rainy, 6 partly cloudy, 3 sunny, and 2 cloudy days in September. The rains are usually heavy. September as well as January, February, March, and April is considered the most uncomfortable time to visit Bronnoysund.