On an 85-degree day it takes only 10 minutes for the interior of your parked car to climb to 102 degrees. In a half hour, it can reach 120 degrees. And leaving windows partially open doesn’t drop the temperature inside the vehicle.
Keep in mind your dog has a higher body temp than you do and she can’t cool down as efficiently as you do, either. Your dog is designed more for insulation from the cold than cooling down in the heat.
You have sweat glands all over your body, but your dog’s are confined to her nose and the pads of her feet. A dog that is heating up can only normalize her body temperature through panting, which just doesn’t get the job done under extreme conditions. In a very short period of time, an overheated dog can suffer critical damage to her brain, heart, liver and nervous system. http://healthypets.mercola.com/sites/healthypets/archive/2013/06/24/overheating.aspx?e_cid=20130630_SNL_TPA_1&utm_source=snl&utm_medium=email&utm_content=tpa1&utm_campaign=20130630