I don't always agree that it's NEVER ok to leave an animal in a car for any amount of time for any reason. I think there are several factors to consider; length of time, temperature, shade or sun, whether the car has A/C that was used, breeze, etc.

I have, on rare occasion, needed to leave a kitty or two in my car. However (before you all go rabid on me saying I'm a horrible cat owner), I had known in advace I would be stopping for 15 minutes or less by the clock (depending on outside temperature), and had cranked the A/C to Artic temps prior to arriving at my destination. If anything my kittes were cold since they were always curled up napping, no panting, no distress, and the vehicle was always still cool inside when I returned. I don't crack open the windows as it lets the heat in, and I park in the shade if possible, or if not then I make sure it's a much shorter stop or make a separate trip if necessary without the cats if it's too hot out.

In the case of seeing other people's animals in cars, I have been known to report some. In those cases the animals were in obvious distress, heavy panting, outside temps were dangerous levels, etc.

I always use the theory of 'how long would I want to sit in that car without the A/C on'. I have never left my kitties in a car longer than I myself would have been comfortable sitting in like that.