Brazil is a huge country with many different climatic zones and can be visited all year round. Therefore, the best time to go depends on the destinations you are visiting on your itinerary and your particular preferences.
Generally speaking, however, the warmest time of year is November to March with temperatures increasing the further North you go. During these months it is not uncommon to be more than 40 degrees. We have found that the slightly cooler months of September and October are a nice time to travel.
The Amazon is hot and humid all year round, but slightly cooler the first half of the year (January until June) which is also the wetter half of the year. The wettest months in the Amazon are March to May. In the wet season there are more activities available by boat and in the dry season there is more chance to hike.
In the North East of the country May and June are usually the wettest months, but as it is close to the equator the temperature does not vary dramatically year round, remaining hot.
Carnival is usually around February and is another popular time to travel with bookings needing to be made well in advance. Spring time from September to October can also be a nice time to be in Rio.
The Pantanal can be visited most of the year offering something different in each season. Generally, however, it is best visited during the dry season that runs from mid April to October. The best time for spotting Jaguars is between June and August which are the driest months where the animals flock to the rivers to drink. July to September is also a good time for bird watching.