August to October is whale season, when humpbacks arrive with their calves and congregate in the waters off the island. This is the most sought-after time to visit, and accommodation books up early. Book several months in advance if you want a specific set of dates in September.
The rest of the year is not a consolation prize. Marine life, birdlife, jungle walks, and snorkeling are excellent regardless of month. The island's ecology doesn't take a break.
Humidity sits at around 98% all year — this is one of the wettest places in the Americas. Expect intense rainfall, daily mist on the upper forest, and stretches where the island seems to be generating its own cloud. Equally, blazing tropical sun can appear without warning. Pack for both within the same day: light layers, waterproofs, and sun protection all earn their weight here. Wrap your bag in plastic for the boat crossing; it will spend time on deck regardless of conditions.
There is no dry season in any meaningful sense, so there is no bad time to visit. The island rewards patience with weather, and the mist that wraps the forest summit is part of what makes it feel like the end of the world.