Hmm, since someone else already got to my pemmican suggestion, I will offer an alternative:

In really cold weather, I like sausage meats, like pepperoni, slim jims, salami, along with good cheese like gouda or cheddar or paremesan. Something peppery helps heat up the body along with regular applied heat. I often pack a small Hickory Farms summer sausage and a few babybel cheese rounds or some string cheese.

Peanut butter is always a good staple.