September in Cap-Haitien is the hottest month of the year. In September, the weather in Cap-Haitien is typically hot. Average daily high temperature in September is about 30 degrees above zero. On average, Cap-Haitien has 16 rainy, 10 sunny, and 4 partly cloudy days in September. The rains are usually heavy. September as well as May, October, and November is considered the most uncomfortable time to visit Cap-Haitien.