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