Frigidaire Freezer Runs Warm in Cold Weather

Question

I have a Frigidaire Fridge/Top Freezer that I keep in my unheated garage. During the winter, it seems that the Freezer (turned to the lowest setting) tends to thaw when the garage is cold (probably 30 to 35 degrees). Ironically, the freezer works great in hot weather! The unit is three years old and this is the third winter I've experienced the problem. Any ideas?