Cracked windows don't cut it - especially with the temperatures that accompany summer weather. Every summer I see this around the city here in Portland, I call the Police every time, it is a $1000 fine here and they will break into the car. Thank you Oregon Police department! Get your police numbers on your cell phones folks so its handy and you can expedite a call.
A car becomes an oven on warm days - you wouldn't leave your dog in an oven - be safe, leave your dog at home.
There are very few people who would ever consider placing their dog into an oven, closing the door, and turning on the heat.
Bottom line - don't leave your dog inside of a car on a warm day. I am and have always been an advocate for animals, our silent sufferers.
"A hot oven or a hot car...It's the same thing".