Make sure you have adequate medical insurance for your personal and travel needs, and that you have funds to cover any medical emergencies.
Yellow fever vaccination is not a requirement but is recommended. Remember to get vaccinated 10 days before your trip.
The mosquito-borne Zika virus is present in Brasil, you should take steps to avoid being bitten by mosquitos when you can.

Crime rates in Brazil are high, especially in urban areas. It is recommended to be cautious and avoid flashing valuables.
Simple robberies on public transportation, armed assaults on pedestrians and car theft are frequent during the day and especially at night.

Requirements to enter Brazil depend on your nationality. Check the specific entry requirements according to nationality here.

https://www.visitbrasil.com/key-information/visa-and-documents-required.html

Brazil is a very large country so its climatic conditions vary, however, it is mostly tropical, meaning that there is not much variation between seasons. Cities like Rio de Janeiro and its surroundings can be extremely hot, but others further south like Sao Paulo and Brasilia have a more moderate climate: it can even get cold.

Brazil is the only country in Latin America whose official and national language is Portuguese. Spanish or English as a second language is taught in schools, and sign language was legally recognized in 2002.

Electricity voltage in Brazil varies between 110V and 220V, depending on the location. Electrical transformers and adapters are easy to find and hotels generally offer them.