The dry season runs from May through October — sunny, warm and reliable, with daytime temperatures around 28–30°C and cooler evenings. This is the peak time for diving, snorkelling, and the lemur-watching trips that require dry forest trails.
November through April is the wet season. December and January bring heavy tropical rain and the risk of cyclones, which can shut down boat trips for days at a time. Hotel rates drop sharply and the island is greener, but be prepared for downpours and consider buying refundable tickets.
The festival of the Donia music week in late May or June brings the island's biggest crowds and best concerts. Easter is when many Malagasy holidaymakers visit and hotels fill up.