If you hate roasting in your car after it’s been sitting in the sun, this one’s for you.

Hannah Fry is a well-recognized math professor at Cambridge University, broadcaster, and science writer. Among her many professional accolades, she earned her Ph.D in fluid dynamics and hosts Google’s Google DeepMind: The Podcast. While she ponders complex concepts daily, she’s quite down-to-earth…and she’d rather look awkward to bypassers than wait for a sweltering vehicle’s HVAC to kick in.

How to cool your boiling hot car in seconds

First, she explains, don’t even bother turning on the air conditioning. “That would take about five minutes…not worth it.”

Instead, open the right rear window. In the U.S., this is the window diagonal to the driver’s door.

Then, and “you do look like a bit of an idiot if you do this,” get out of the car, turn around, and very quickly open and close the driver’s door. 

Ta-da!

Fry explains that the reason this method works is called “heat transfer.” Opening and closing the door opposite the open window both drags and pushes the roiling air out. Since it has to be replaced with more air, the air that fills the now-empty space is a fresh, exterior breeze.

Try it out the next time you feel nervous about climbing into a roasting hot car.