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Lock It: Parked Cars Trap Deadly Summer Heat

hot car summer greenhouse effect

Most parents know that leaving a child in a parked car can be dangerous. Even in cooler outside temperatures or with windows lowered, the temperature inside a parked car or truck can rise rapidly. But parents are not the only ones who must take care to prevent this risky situation.

Every driver can reduce the risk of endangering kids to entrapment in vehicles by keeping vehicles securely locked. This prevents curious kids from climbing into a parked car or truck, only to be stuck in the heat when they cannot find their way out.

Heatstroke prevention - child safety - lock your car playground
Share this on Facebook, Twitter or Pinterest to remind your friends and loved ones to take care to prevent heatstroke accidents.

How quickly does the interior of a car heat up on a hot summer day? In our simple test, we watched the temperature climb from 81 degrees Fahrenheit to 108 degrees (F) in just 50 minutes. According to CDC, exposure to such high temperatures – even over a short amount of time – can lead to heat exhaustion or, worse, heat stroke. When body temperature reaches 104 degrees (F), a person is experiencing heat stroke, a medical emergency that requires calling 911.

For our test, we parked in a sunny lot on a 95-degree (F) day. Relatively speaking, our test vehicle should be slow to heat; its white exterior paint should reflect more heat than a darker color, and its tinted windows should minimize the solar energy entering the cabin. Our test car was also parked with its windshield away from the sun. All together, these factors mean the test car should heat up slowly compared to, say, a black car with clear glass and its windshield facing the sun.

hot car summer greenhouse effect child safety heatstroke prevention experiment collage
In our informal experiment, temperatures inside a closed car climbed from 81 degrees to 104 degrees in 30 minutes. The outside temperature was 95 degrees.

Still, in the first minute after the air conditioning was switched off and the car’s doors were shut, the interior temperature had already risen by one degree (F). After 13 minutes, the inside temperature hit 100 degrees (F). At 30 minutes, the deadly 104-degree (F) threshold was crossed.

Even if the interior temperature stopped climbing there, it could still be harmful or even deadly for anyone inside. The temperature continued to rise, though, eventually reaching 108 degrees (F) when we stopped the test. It likely would have continued to rise, though, as long as the sun was out. The surface of the asphalt parking lot we used measured 128 degrees (F) after day-long exposure to the sun.

Heatstroke prevention - child safety - infographic 20 degrees
Never leave children or pets unattended in a parked car. And while Fido is unlikely to open your car door and climb in for a ride, an unlocked, parked car may be irresistibly fascinating to a youngster. Practice smart summer car safety. Be sure to always lock your car, even when parking in your own driveway or where you don’t expect kids to be playing. Remind friends and family members to do the same by sharing this article or images above. You may save a child’s life.

Check out all the vision and safety products available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on summer heat, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Nick Palermo View All

Nick Palermo is a freelance automotive writer and NAPA Know How blogger. Since becoming an auto news and reviews contributor at in 2011, he has broadened his coverage of the automotive industry to include topics like new car technology, antiques and classics, DIY maintenance and repair, industry news and motorsports. A committed advocate for automotive media professionals, Nick is a member of the Greater Atlanta Automotive Media Association.

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