I think given the choice, I would opt for a cheap pup tent as an emergency shelter. In my area, you need a floor and bug netting. This one sells for $18, weighs 3.4 pounds, but you could leave out the metal poles and stakes and make your own on site or hang it off a tree branch. Would get it down to about 2 pounds.

http://www.amazon.com/gp/product/B000P9E...ASIN=B000P9EZPW