Getting Too Hot
Leaving a car battery out in temperatures that are too extreme on the warm side leaves you vulnerable to the very real possibility that you could have a battery that ends up getting corroded. The chemicals within the battery can start to react too quickly to the heat, and that can lead to great damage that ultimately results in the battery being rendered useless.
Getting Too Cold
A car battery that ends up being too cold could result in one that literally has chemicals within it that freeze up beyond any useful measure. You must avoid leaving your car battery exposed to temperatures that threaten this as well.
