Before you plan to visit Brazil decide what it is you want to see. Do you want to see Carnival or do you want to see the real Brazil?

Best Periods to visit :

June (to visit Parintins in Amazonas)
September to February (to visit Santarém in Amazonas)
September to October and March to April (to fish in Araguaia in Goiás)
December to May (to see waterfalls in Presidente Figueiredo in Amazonas)

March and May (rain season in Ceará)
April to September (to visit Serra da Capivara in Piauí)
May and June (a lot of rain in Bahia)
May and August (rain season in Sergipe and Alagoas)
June to July and December to March (to visit Chapada Diamantina in Bahia)
June and July (cold in Gravatá-Pernambuco)
July and August (rain season in South Bahia)
July and January (to surf in Jericoacoara, Ceará)
September to April (to visit Recife)
December to February (summer time in Bahia)
December to January (to visit Sergipe and Alagoas)
December to March (to visit Paraíba and Rio Grande do Norte)
December to July (to visit Sete Cidades in Piauí and Lençóis Maranhenses in Maranhão)

January to April (best time to visit wine-growing in Serra Gaúcha)
June to August (cold in Serra Gaúcha)
July to November (best time to see the whales in "Litoral Sul" de Santa Catarina)
October to March (enjoy the beaches in "Litoral Gaúcho")
December to February (summer time in Serra Gaúcha)

August to May : Rio de Janeiro and surroundings (Buzios, Angra, Paraty)
April (to visit Diamantina in Minas Gerais)
April to November (to visit caves in São Paulo; dryness period in Minas Gerais)
June to August (low season in Campos do Jordão)
June to September (winter in "Serra Fluminense - Petrópolis)
All year - Historic Cities in Minas Gerais (except in school holiday period)
December to March (to visit caves in Minas Gerais)
December to January (to visit Vitória in Espírito Santo)

Central West
May to October (to visit Alto Paraíso in Goiás)
May to September (to visit Jalapão in Goiás and Pantanal)
July to October ( to fish in Pantanal)
November to May (to visit Brasília - capital of the country)
December (to visit Bonito in Mato Grosso do Sul)