September in Marsh Harbour is the rainiest and the cloudiest month of the year. In September, the weather in Marsh Harbour is typically hot. Average daily high temperature in September is about 29 degrees above zero. On average, Marsh Harbour has 18 rainy, 11 sunny, and 1 partly cloudy day in September. The rains are usually heavy. September as well as July, August, and October is considered the most uncomfortable time to visit Marsh Harbour.