a long time ago I was in the habit of winter back packing in the Adirondacks. One memorable trip saw the temp go to -20 overnight. Fortunately I had the proper equipment. Funny thing about equipment ratings is while my sleeping bag was rated to -40F, they don't tell you the rating is really about "survival" not "comfort". But if I'm stupid enough to be out there at -20 I shouldn't expect to be comfortable.
