There has been a lot of controversy over the years about what to do if you notice a pet inside a vehicle on a hot day. We would like to offer some tips that we believe can best help in that situation.
First, take in the scene. How hot is it? Are the windows down? Is the car parked in the shade? What condition is the pet in? A dog can be panting and not be in complete distress. How long has the pet been in the heat? The owner may only be away from the car for a few minutes and not actually harm a pet, so you want to be cautious of how you proceed. You can go to the nearest business to see if they can make an announcement for the owner of the car to return to the vehicle if you have witnessed the animal for more than a few minutes.
If you suspect that a pet has been in the heat too long (say, longer than 10 minutes) and is showing signs of possible heat stroke (restlessness, a dark tongue, excessive panting, lethargy, vomiting, or a lack of coordination), call the police immediately. You could also call animal control, but usually a police officer can get to the scene more quickly to remove the dog from the car. Tell the operator that it is an emergency. Take down the color, make and model of the car, as well as the license plate number and a description of the dog. This information will be important if the owner returns to the car and leaves before the authorities arrive.
If you feel the pet is in severe distress before the police or owner arrives, find a witness to also assess the situation before attempting to remove the dog from the car. Remember to check if any doors are unlocked before breaking a window, as you do not want to damage property if possible. Be aware that not all pets are friendly, so proceed with caution. Be prepared with a leash if you are going to remove the pet from the vehicle. Offer cool water and shade. If you believe the animal's life is in danger, take them to the nearest veterinarian after leaving the owner a note as to where you are going and with your contact information. It is important to stay with the pet until the situation is resolved.
As pet owners, we love to spend time with our "babies," but we have to keep their safety and well-being in mind. If you are going to take your pet with you in the car, try not to leave them alone. Go through a drive-thru if possible, park in the shade with all windows down (or better yet, with your air conditioning on, though neither of these are guarantees of safety) if you are going into a building for less than 5 minutes, or shop in stores that allow pets. The best possible solution is to leave your pet at home on warm days. It is simply not worth the risk.
To give you an idea of just how sweltering it can get in a car, check out this video from Dr. Ernie Ward. He sits in a parked car for 30 minutes with all four windows cracked, on a 95 degree day.
Keep in mind that it does NOT have to be in the 90's to be too hot for your dog in the car. This chart shows that at just 70 degrees, it can get uncomfortably stuffy inside a vehicle.