Teresópolis has a mild mountain climate year-round, with temperatures typically 8–10°C cooler than Rio de Janeiro below. The dry season runs from May to September — these are the best months to visit. Skies are clear, humidity is low, and the park trails are in good condition. July and August can feel cold at night, especially at altitude in the park, so bring warm layers.
The summer months (December to March) bring heavy afternoon rainfall — a tropical mountain pattern where mornings are often clear but clouds build rapidly after noon and thunderstorms are common by late afternoon. Hiking in summer can be wet and slippery, and flash flood risk in the park is real. That said, the waterfalls are at their most impressive and the forest is lush. The Christmas and Carnival periods see a big influx of Rio day-trippers; weekends generally become noticeably crowded.
The park is open year-round except in the event of extreme weather warnings. Midweek visits avoid the weekend rush from Rio.