The UK is currently experiencing a severe heatwave, with red alerts issued across more than 50 areas. Cars quickly become unbearably hot, making entry unpleasant. While many reach for the air conditioning, a simple trick—backed by science—can cool the vehicle faster and more efficiently.
The Hack: Open Window, Pump Door
Capital FM presenter Sian Welby shared the tip, originally from Professor Hannah Fry. The method: wind down the back left window, then get out and rapidly open and close the driver's door four times. After re-entering, the car is noticeably cooler. The technique relies on fluid dynamics: each door movement creates a low-pressure area that draws hot air out through the open window, replaced by cooler outside air.
Scientific Explanation
Professor Fry explained in a YouTube video: "When you open and close the door quickly, it sweeps out air, creating low pressure. This sets up bulk flow, drawing hot, sweaty air out. The only way to refill is with fresh air from outside. It takes two or three goes, and suddenly it's beautifully temperate." She noted that while you might look "a bit of an idiot," the method is far more effective than air conditioning.
Public Response
The video received many grateful comments. One user said: "I used to do this without knowing the science—it just seemed like the thing to do and it helps." Another wrote: "Been doing this for 20 years with the blind belief that it's better than just opening all the windows. Thanks for the scientific pardon." A third added: "This is a top tip, I've been doing this for years and can absolutely confirm it works as described."
