I've heard it said that down is best for very cold, dry environments while synthetic is better for warmer, wetter climates. We all know that the Pacific Northwest is certainly not dry. I've got to wonder though... just how cold can it really get here? Seriously, this isn't Alaska or Tibet. If you, by some gross error of judgement, get caught on top of Ranier and the Mother of all storms comes rolling though what's the worst you can expect temperature wise? 0F? Just how warm do our clothing and sleeping bags really need to be before it becomes overkill?