On a welcome spring day, with the temperature no more than 70 degrees, a dog owner heads out on errands with his dog. The first stop the home supply store, no dogs allowed. He leaves his dog in the car. There is a line and a 20 minute wait. The likely temperature inside the car when he returns: 99 degrees. Another 20 minutes and the dog could suffer potentially lethal heatstroke if his core body temperature reaches 108 degrees.