September in Basseterre is the rainiest and the hottest month of the year. In September, the weather in Basseterre is typically hot. Average daily high temperature in September is about 29 degrees above zero. On average, Basseterre has 15 rainy, 11 sunny, 3 partly cloudy, and 1 cloudy day in September. The rains are usually heavy. September as well as May, October, and November is considered the most uncomfortable time to visit Basseterre.