I think Clif bars are the ultimate in temp resistance. some years ago, within a one-week period I had some along for snacks on a snowshoe hike north of Anchorage with some pals. at -25, I could still bite into them, while my buds discovered that their blocks of cheese and pepperoni had converted to concrete. a few days later, I was on a trip in Costa Rica hiking. after 6 hours in the luggage area of a bus, my Clif bars were unchanged, while energy bars and candy bars in other peoples' packs had liquified.
Clif bars even taste almost OK, though some kayaking buddies insist on calling them turd "bars." I do admit that they do look a lot like dog output, but no effect on flavor.