Chapada dos Veadeiros in October

April through September gives you the sweet spot — dry season with clear skies and full-flowing waterfalls. May and June are particularly perfect: daytime temperatures hover around 25°C, nights drop to a comfortable 15°C, and you'll have brilliant blue skies almost every day. July and August bring more crowds, especially during Brazilian winter holidays, but also guarantee the best weather. The dry season means easier driving on dirt roads and better visibility for those sunrise hikes to Mirante da Janela. October through March is rainy season, which sounds bad but isn't necessarily. Sure, some roads become impassable and afternoon thunderstorms are common, but the landscape explodes in green and many waterfalls reach peak flow. Plus, you'll have the place mostly to yourself and pay lower accommodation prices. Just avoid December and January when Brazilian families descend en masse for summer holidays.