Andasibe is a year-round destination, but timing matters. The forest receives around 1,700mm of rain annually — roughly 200 rainy days — so there is no real dry season. The wettest months are January to March, when heavy rain can make trails muddy and some routes slippery. The coolest and driest period runs from June to October, when daytime temperatures hover around 16–20°C and the nights drop to near 10°C.
The best time for indri viewing is probably May to October, when the animals are most vocal and the forest paths are at their most manageable. Frog diversity peaks in the wet season (November to April), when dozens of species breed in the temporary pools. Chameleons are present and findable year-round on night walks. If you plan to visit Mantadia, the dry season road conditions are significantly better.