September in Honolulu is the hottest month of the year. In September, the weather in Honolulu is typically hot. Average daily high temperature in September is about 28 degrees above zero. On average, Honolulu has 12 sunny, 9 rainy, 8 partly cloudy, and 1 cloudy day in September. The rains are usually light. September as well as March, April, May, and June is considered the most uncomfortable time to visit Honolulu.