The Dangerous Heat Trap Inside Your Car

On a warm day, your car can turn dangerous faster than most people realize.

As meteorologist Sara Tonks warns, “temperatures in your car can easily climb by up to 40 degrees within just an hour of being left out in the sun.”

That means an 80-degree day can quickly become 120 degrees inside your vehicle, and even hotter if temperatures outside are already high.

Here's why it happens, what you should know and how you can keep your car and its passengers safe.

The process starts as the sun’s shortwave radiation enters your car through the windows. That energy heats up surfaces like seats and dashboards, which then release longwave radiation in the form of heat.

But here’s the problem: “That radiation can't easily pass through glass,” Tonks explains. So it gets trapped, bouncing around inside and creating a rapid heat buildup.

(MORE: Everything You Need To Know About Heat Safety)

“Your car does work exactly like a traditional greenhouse,” Tonks adds. The result is a feedback loop where heat keeps building with nowhere to go, causing temperatures to spike quickly.

Cars can reach 140 to 150 degrees under extreme conditions. And yes, that's hot enough to cook an egg or bake a cookie.

“The problem there isn't just how hot it gets, but how fast it does it,” Tonks notes. Even a “quick” errand can turn into a dangerous delay, putting groceries, electronics, pets or children at risk inside your vehicle.

Tonks also warns that cracking a window won’t save you, comparing it to opening an oven door: “It's still going to be an oven, and it is still going to be very hot inside that oven."

(MORE: Summer Is Hard On Your Car, Here’s How To Take Care Of It)

Some additional factors that affect the temperature inside your car:

• Dark-colored cars and seats absorb more heat and warm faster.
• Tinted windows can help by blocking some sunlight before it enters.
• Cloud cover can slow heating by reducing incoming sunlight.
• High humidity can make it feel even hotter inside the car.

Tonks stresses awareness. “We're all human, we all make mistakes,” she says, which is why it’s important to build habits like placing a reminder in the front seat if a child or pet is in the back, or always using drive-throughs for errands instead of exiting the car entirely.

But her best advice is simple, especially as the weather gets warmer: Never leave a child or pet in a parked car for any reason or any amount of time.