Everyone targets summer dec-mar for reveillon (new year's) and carnival but cara, it's 40°C with 80% humidity plus 2 million tourists and hotel prices that'll make you cry. Like seriously, copacabana reveillon brings 3 million people to one beach.

April-june is quando os cariocas actually enjoy their city. Temperature drops to perfect 25-28°C, zona sul beaches become liveable again, and hotel prices in ipanema/leblon drop 50%. You can actually get a table at aprazível (santa teresa) without reserving 2 months ahead. Only trade-off is afternoon chuva but usually quick tropical showers, não those biblical storms that flood lagoa rodrigo de freitas.

Carnival is epic if you buy blocos tickets in advance but literally everything shuts down for 5 days — Supermarkets, museums, even most restaurants in zona sul. Plus accommodation prices triple and boa sorte finding anything in copacabana without booking a year ahead. If you want to actually explore tijuca forest, visit pão de açúcar, or eat at proper carioca botequims, come literally any other month, sabe? The city belongs to locals again after march.