If you're hoping to get lost in the rain on your romantic getaway, take a look at these details about year-round temperatures in Puerto Iguazú: The hottest months are usually January and December, with an average temperature of 26°C, while the coldest months are July and June, with an average of 18°C. The rainiest months in Puerto Iguazú are October, January, December and May, with each month seeing an average of 212 mm of rainfall.