UT Dallas Magazine

How Hot Is It? Enough to Cook Items in a Car


The North Texas summer can take a toll on anything or anyone left in a closed-up car. But just how dangerously hot can it get?

During a recent string of days with high temperatures in the triple digits, a UTD team set up a demonstration to paint a more tangible picture of the effects – both damaging and tasty – on items in an enclosed, overheated space.

With near-record high temperatures predicted, Wednesday, July 18, was ideal for the informal experiment. At 9 a.m., a car was parked in an uncovered lot under mostly sunny skies with temperatures in the 80s and rising.

Inside the car on its dashboard sat two trays of items: lipstick, three crayons, milk in a plastic sippy cup, hot dogs and buns, cookie dough, sliced tomatoes, and various cheeses on crackers. A potted basil plant was included, along with a digital thermometer.

By 4:30 p.m. – after nearly 8 hours – it was 108 degrees in the Texas air. Inside the car, the temperature registered 180 degrees with a thermal imaging camera.

The time-lapse video illustrates the power of extreme heat on the items. The results:

  • The red lipstick and red, orange and yellow crayons had melted into colorful puddles.
  • The cookies were cooked, with firm edges and a chewy inside. (Always follow the FDA guidelines concerning eating undercooked cookie dough.)
  • The temperature of the milk rose from 74 degrees in the morning to a whopping 170 degrees.
  • The tomatoes – now sun-dried and shriveled – were delicious, according to one taster.
  • The basil plant’s leaves were completely desiccated.
  • The hot dogs* looked like they had just come off the grill, without the char marks. The buns were dried out.

Dr. Mary Urquhart, an associate professor of physics and head of the UT Dallas Department of Science/Mathematics Education, emphasized how quickly extreme heat can do permanent damage to any living creature.

“Leaving things in a car, particularly in the summer, is dangerous,” she said. “Small children and pets are particularly vulnerable. Due to their small size, they will heat up very quickly as the temperature rises inside the car. People can even get burns from the dashboard of a car that’s been sitting in the sun.”

“Cracking your windows to allow air to flow through a parked car is about the only thing you can do to reduce the heat, but when it’s over 100 degrees outside, it’s still going to be very hot inside,” she said.

And the heat goes on. Triple-digit high temperatures are projected in the area for several more days.

* The USDA says never leave hot dogs at room temperature for more than 2 hours and no more than 1 hour when the temperature goes above 90 °F