A woman posted the following on an online forum:

We all know how deadly a parked car can be even on a mildly warm day. However, I have been known to leave the car running AND LOCKED with the AC on for The Dog. Makes me laugh when I come back to the car and he’s sitting there so proud and easy with his fur flying back from the fan blowing full blast.

As long as I have lived in the desert I've had dogs with me whether it's running errands, going to work or out to play. A dog's there. I have also learned that living in the desert presents special problems for dogs on the ground and in cars. So about a year ago I ran this experiment to find out what the interior temps of a car could get up to.

On April 19, 2009 at 10:32 AM I placed a Fluke K type thermocouple and digital thermometer in my car with the sensor element suspended in the air in the center of the passenger compartment. Opened all of the windows and the sunroof and let it sit until the temps equalized inside and out.

Time 10:15: Starting temp 85F inside and out.
Closed the car, all windows and the sunroof. Put up the window shades in the front window and closed the shade for the sunroof. Car now dark inside. Wait fifteen minutes. Time: 10:32am Check temp with shades in place. Outside air temp still 85F. It was 105F inside the car.
Step 2: Removed windows shades. Let the temps equalize and run a second test for 15 mins. Close car at 10:35. Next check time 10:51. The outside temp was no 86F. INside the car it was 111 without the shades. Those temps can kill not only a dog but a child as well. Add to that there are laws about l leaving dogs and people in cars. If you thinks it's difficult to breath on a still day when it's 110F outside think about what it's like in a car with no ventilation.

Desert rules for dogs in cars.
Rule 1: Do not leave your dog in the car. If you're not in the car your dog should be either; open windows or not.

Since that probably won't be heeded here are some more good rules.

Rule 2: Run the A/C set at max A/C vents pointed to the roof.
Rule 3: There is no rule 3.
Rule 4: To keep your car from overheating open the hood all the way. This allows heat to escape.
Rule 5: Always park in the shade with the back of the car pointing to the sun or where it will be.
Rule 6: Use a sunshade in the front window, cover sunroof with towel and leave it open 2".
Rule 7: Leave windows open a few inches.
Rule 8: Leave a large bowl of water.
Rule 9: Use terry towels or seat covers on leather seats.
Rule 10: Leave your dogs home on hot days because it's still against the law to leave them in the car A/C or not.

"But I want to have my dog in the car."

To be totally redundant; during the spring and summer anyone person or dog left in a closed car can die within half an hour. The only way I would ever leave a dog in a car is with a police K-9 A/C setup. Even then you run a risk if something goes wrong with the system. It is against the law to leave a person or pet in a car when the temps are elevated, about 80F maybe a bit more.

To prepare your car for dogs in summer (that would be a good name for a band) have your A/C and cooling system completely and thoroughly overhauled and serviced. Inspect all hoses replacing those that are marginal and the radiator flushed and rodded if necessary. Note that some K-9 cars I've seen have a thermostatically controlled door relay installed. If the temps in the car go over a preset level the doors automatically open allowing the dogs out and fresh air in. Considering the technology today that's something that should be fairly easy to find or make.

The thing is despite warnings on radio and TV people still leave there pets and children in the car when it's hot out. If I see it whether your A/C is running or not I call the cops or animal control. Last word. If the temps are over 80-85 and you can't take the dogs out of the car when you park...

LEAVE THEM HOME!!