September in Huatulco is the coldest month of the year. In September, the weather in Huatulco is typically warm. Average daily high temperature in September is about 26 degrees above zero. On average, Huatulco has 26 rainy, 3 cloudy, and 1 sunny day in September. The rains are usually heavy. September as well as June, July, and August is considered the most uncomfortable time to visit Huatulco.