This isn't a suggestion . . . It's a rule here in Tucson and probably throughout most of Arizona. You don't leave your dog in the car alone. EVER. Not for a few minutes -- not for a few seconds. NEVER, EVER AT ALL. There's simply no variables and I'm sure that's so there's no discrepancies or misunderstandings as temps can rise to dangerous and fatal levels so very quickly here.
Need I add you don't leave children unattended in cars either? EVER.