I live in SW Montana at 5500 feet on the Divide. Last year the temps were below zero for most of the rifle season and the winds were terrible. I never camp out any more since I live where I hunt but I can't imagine sleeping in anything that isn't truly capable of -15 weather at a minimum in the winter. Being rated at zero usually doesn't mean that you're warm at zero degrees, you'll need something rated for at least 10 degrees colder just to be warm in zero degrees. I hunted several days in -20 to -30 temperatures last year.
