They are 100% waterproof; that means no water in, no water out. Don't think that you're going to be able to hike around in this stuff without building up condensation inside. It's made to keep the rain off, and it'll sure do it, just make sure you've got all the vents open when you go for a walk! They are also very quiet for rain gear and extremely durable (although not indestructable as they lead you to believe).