September in Zihuatanejo is the rainiest and the coldest month of the year. In September, the weather in Zihuatanejo is typically hot. Average daily high temperature in September is about 28 degrees above zero. On average, Zihuatanejo has 26 rainy, 2 sunny, and 2 cloudy days in September. The rains are usually heavy. September as well as July and August is considered the most uncomfortable time to visit Zihuatanejo.