Rain falls year-round. The three wettest months are January, June, and July. The three driest are February, April, and November. Monsoon-type storms can lash the region at any time; rain invariably falls more heavily in the late afternoon and at night. August through November are best for turtle-watching.

The interior of the park is hot, humid (very humid on sunny days), and windless. Bring good raingear; a heavy-duty poncho is ideal (the lodges provide these for guests). It can be cool enough for a windbreaker or sweater while speeding upriver under cloudy weather. Take insect repellent--the mosquitoes can be fierce.(you'll need Avon's Skin-so-Soft for these, or better yet DEED)