His dealer said he wasn't the only one. He put a thermometer on the new hood to see how hot it could get. While only a few batteries will blow up at high temperatures, they all may be damaged by the heat. Their useful life will be shorter and their capacity reduced. Which means the car will be harder to start in cold weather.
Cold weather makes batteries sluggish.
The chemical reaction in the battery that produces the electricity slows down in the cold. Cold batteries resist being charged - require a longer than normal charging time. If the next morning is going to be unusually cold, charge your battery the night before. Newer cars have one or more on-board computer systems that use electricity even when the car is not running. We make float chargers that will keep up the battery of a seldom used car.