Erawan National Park in March

November through March offers the perfect combination of cooler temperatures and full water flow. December and January are peak months — expect crowds but also the most spectacular waterfalls. April and May are scorching hot, but you'll have the pools mostly to yourself. Avoid June through October when heavy rains make upper trails dangerous and muddy. The waterfalls still flow during dry season, but the pools shrink considerably by April. Early morning visits (8-10 AM) give you the best light for photos and fewer people competing for swimming spots.