The best time to visit Chapada Diamantina is the dry season, roughly May to October. During these months the trails are dry, the rivers are lower and clearer for swimming, and the heat (25-32°C) is manageable with early starts. July and August are the peak tourist months, particularly for Brazilian visitors on school holidays; advance booking for pousadas is advisable.
The wet season (November-March) transforms the park: waterfalls are at their most powerful, the vegetation is lush green, and some of the swimming holes are flooded beyond use. The Cachoeira da Fumaça reaches its maximum flow and noise in January-February. Trails become muddy, some routes close, and river crossings can be dangerous. But for waterfall photography and botanical interest (many flowering species bloom in the rains), the wet season has its own rewards.
The Poço Encantado blue light phenomenon occurs at its best between April and September, when the sun angle is low enough to enter the cave; outside these months the effect is less dramatic or absent.