Corcovado National Park in September

December through April offers the driest conditions, but 'dry' is relative in a rainforest that gets 200+ inches annually. January and February see the least rainfall and calmest seas for boat transfers. March and April heat up significantly — temperatures hit 95°F with crushing humidity. But wildlife viewing peaks during dry season when animals congregate around water sources. The shoulder months of November and May offer fewer crowds and still-manageable weather. Avoid September and October when rivers flood and trails become treacherous. Morning hours provide the best wildlife activity regardless of season. Plan for 6am starts — the forest comes alive before the heat sets in. And remember, weather can change instantly. That sunny morning can turn into a torrential downpour by noon.