Cold will kill you, but most deaths happen in the 50s and even the 60s due to hypothermia. Once your core temp starts to drop you lose the ability to think straight and you start making bad decisions. The best way to keep the core up is what backpackers call "vapor barrier insulation" and pay $100 for a pair of socks and which my poor old granny called "bread bags" and conjured up at no cost. So, when it really counts: Bread bags for socks and mitts; a coverall made from the roomiest can liner that you can find (55 gal min). Make the cover all by pulling the liner over your head and position it so that the liner corner fits neatly over your skull and the crown of your head. From the liner corner use your extended hand and fingers to measure down one side of the liner to point "A" and a second time to find point "B". Tear the liner seam from "A" to "B". This gives you a pointy "KKK" corner keeping your head dry with your face peering out of the "AB" slit. The liner will nearly reach the ground and you will be incredibly warm. Anything against your skin is going to quickly become wet with persperation. Ideally you can have a layer of thin material against your skin (socks, undies, tee shirt); then the liner; and finally your pants, shirt, coat, hat, etc. Make this up before needed so that you don't wish that you had. Stuff garbage bags everywhere but especially in your car.