In September, the weather in Foz do Iguaçu is typically warm. Average daily high temperature in September is about 25 degrees above zero. On average, Foz do Iguaçu has 14 sunny, 11 partly cloudy, and 5 rainy days in September. The rains are usually moderate. September as well as August is considered the most comfortable time to visit Foz do Iguaçu.