A: Every year in United States, approximately 30 to 40 children die from heatstroke after being left in cars. You usually hear warnings about not leaving children in the car during the summer. But a recent study found that the air inside a car can heat up quickly in mild weather, in the low 70s, as well as hot weather, in the high 90s. The study found that the air temperature rose 19 degrees in the first 10 minutes and 34 degrees within 30 minutes. Opening the windows a crack or running the air conditioner before turning off the ignition didn't keep the car cooler. And a car's color didn't even make a difference.

Cars heat up quickly because they're like greenhouses. The sun's rays pass through the windshield and windows and heat the dashboard and seats. This gives off heat to the air, and the hot air can't escape. Young children's bodies heat up three to five times quicker than adults because they're so small, and they don't sweat to cool down as well as adults.

A study of children who died of heatstroke in cars found three different circumstances: either parents intentionally left their child in the car while they did something else; parents forgot that their child was in the car when they left it (e.g., they thought they had dropped off the child at daycare, but they hadn't); or children went into an unlocked car or car trunk to play and got stuck there.

Recognizing this danger, many states have passed laws against leaving young children unsupervised in a car. Parents need to know the following:

• Never leave a young child alone in a car, even in mild weather, and even for a quick errand. This is not only dangerous because of heatstroke, but also because a child could release the parking brake and cause the car to roll and crash, or the child could be abducted.
• Always know when your child is in the car with you. It's safest to have your child in her car seat in the back seat, but be sure to have a reminder up front with you. For example, you can leave a stuffed animal in your child's car seat when it's empty; and when you put your child in the car seat you can bring the stuffed animal into the front passenger seat.
• When your car is parked, keep it locked and keep your keys out of your children's reach. Never let your child play in a parked car or trunk, even in your own garage.