Should you leave your car windows open during a heatwave? What drivers need to know

Drivers have been advised against leaving their car windows slightly open while parked during the UK heatwave.

Parking marketplace YourParkingSpace says cracking the windows is unlikely to prevent dangerous heat building inside the vehicle and could leave it less secure.

The advice comes after the UK recorded its hottest June day on Thursday, with temperatures expected to remain as high as 32°C in parts of the country on Friday.

Peer-reviewed research found that the temperature inside a parked car increased by an average of around 22°C within an hour, with 80 per cent of the rise occurring during the first 30 minutes.

Tests also found that leaving the windows open by around 4cm did not significantly slow the rate of heating or reduce the maximum temperature reached.

Current public-health guidance similarly warns that leaving a window partly open is not enough to keep a parked vehicle cool or make it safe for a person or animal to remain inside.

Larne O’Donoghue, spokesperson at YourParkingSpace, said: “Leaving the windows slightly open might seem like an obvious way to keep a parked car cooler, but research suggests a small gap makes very little difference.

“It can, however, leave the vehicle less secure, so drivers should close all windows and the sunroof completely whenever the car is unattended.

“Choosing covered or underground parking where available can reduce exposure to direct sunlight. Planning ahead also gives drivers greater choice over location, price and walking distance, while pre-booking means they know exactly where they are going and do not have to circle around searching for a space in extreme heat.

“When returning to the car, drivers should open the doors and windows briefly to release trapped hot air before getting inside.”