I was in North Dakota for four years when I was in the Air Force. We kept C-rations or K-rations, I can't remember, in the trunk, but it remained below freezing for months at a time. :-> I'd eat the survival food somewhere along the line every summer, just to rotate it out. A winter in the trunk did no damage. Again, the the freeze/thaw cycles were really stretched out, and I don't know how it compares to Tahoe.