Usually its a bad idea to dischare an SLA at anything below -4F (-20C), or charge it at anything lower than 5F (-15C). Ideally they work best at 68F - 72F (20C to 25C) both discharge and charge. But in a car the same would apply @ heat. They don't like to be charged at higher than 122F (50C) or discharged higher than 140F (60C).
Running them too cold results in physical plate breakdown and damage. Running them too hot results in an accelerated drying up the chemicals in the battery, and shorter life span. They may also swell when too hot.