I was going to write about this, but they have done such a great job, I copied this information and the links from The Humane Society Of The United States web site posted on May 22, 2014.
What to Do If You See a Pet in a Hot Car
It may take only minutes to save a life
Leaving pets locked in cars is never safe. But when the weather gets warmer, it can be deadly. Pets can't withstand high temperatures—they can cause irreparable organ damage and even death.
How to help a pet left in a hot car
• Take down the car's make, model and license-plate number.
• If there are businesses nearby, notify their managers or security guards and ask them to make an announcement to find the car's owner.
• If the owner can't be found, call the non-emergency number of the local police or animal control and wait by the car for them to arrive.
Other ways to help
• Get informed: Learn your town's laws about leaving pets in hot cars now.
• Get ready to call for help: Gather the essential telephone numbers and have them on hand. You’ll want to have your local animal-control agency's number and the police department's non-emergency number so you can quickly report the situation. Keep these numbers in your purse, your car's glove compartment or programmed into your phone.
• Spread the word: Distribute The Humane Society of the United States hot car flyer, which spells out the dangers of leaving pets in parked cars. Order more flyers on animalsheltering.org. You can also watch and share our retro video on the issue.
• Get involved: Ask local store managers, shopping malls, restaurants and other businesses to post signs asking customers not to leave their pets in their cars while shopping, dining or engaging in other activities.
• Speak up: If your town doesn't have a law prohibiting leaving pets in parked cars, contact your local representatives or attend a town hall meeting to start lobbying for one. Learn the basics about advocating for animals with our activist toolkit.
The greenhouse effect
It doesn't have to be that warm outside for a car to become dangerously hot inside. Here are some facts:
• When it's 72 degrees Fahrenheit outside, the temperature inside your car can heat up to 116 degrees Fahrenheit within an hour.
• When it's 80 degrees Fahrenheit outside, the temperature inside your car can heat up to 99 degrees Fahrenheit within 10 minutes.
• Rolling down the windows has been shown to have little effect on the temperature inside a car.
Hot Car Flyer (PDF) link