Tradtusker. If you're going to be bow hunting in Colorado, that means September, and quite frankly, it's usually dry and quite warm, sometimes very warm in September, even in the mountains. You might have a couple days out of the month with some cold temperatures and rain or snow. A bag rated for 20 degrees will be plenty. Go with one rated for 0 degrees if you're cautious. I've been backpack hunting for about 30 years now and have used down bags the entire time. Can't say as I ever got one wet, including two weeks of solid rain in Alaska. Folks have already given good advice re how to keep a bag dry. Given where you'll be hunting, the time of year, and a modicum of woodmanship skills, a wet bag is a non issue. Happy hunting.