Planning for the weather is a good way to make your trip to Foz do Iguaçu relaxing and enjoyable, especially when you're splurging. The hottest months are usually January and December with an average temp of 79°F, while the coldest months are July and June with an average of 65°F. The rainiest months in Foz do Iguaçu are October, December, January, and May, with each month seeing an average of 8 inches of rainfall.