Planning for the weather is an important factor for making your trip to Petrópolis a success, especially when you're splurging. The hottest months are usually February and January, with an average temperature of 25°C, while the coldest months are July and June, with an average of 20°C. The rainiest months in Petrópolis are January, December, November and March, with each month seeing an average of 255 mm of rainfall.