The staggering speed the temperature inside a locked car can rise has been captured on video.
The footage, released by motoring organisation the NRMA, shows the inside temperature of a locked car can climb by as much as 70 per cent in just minutes in the summer heat.
The tests were done over three days last month, amid a surge in people accidentally locking people and pets inside cars.
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On one day the temperatures rose by nearly 20C in an hour - from 24C to 42C - an almost 70 per cent increase.
NRMA road safety expert Dimitra Vlahomitros said the experiment should be a serious warning.
"On the 28C day the inside temperature reached 48C, but our camera overheated at 45.5C and stopped working – fortunately this was an experiment and not a real-life scenario with a child in that seat," Ms Vlahomitros said.
"Parents need to be reminded that although it's tempting to leave the kids in the car while quickly grabbing a coffee or paying for petrol, the risk of an accidental lock-in is too serious.
"If a child is stuck inside a car while the temperature is rapidly rising, they can very quickly become distressed, dehydrated and even die from organ failure."
Over the past year, the NRMA has rescued 1500 children and babies and 1400 animals from vehicles in NSW and the ACT.
October was the busiest month, with 164 calls.
NRMA roadside patrol team leader Kosta Karavanas said he had noticed an increase in parents accidentally locking kids in cars with keyless entry features.
"With some car models, as soon as the key is inside the car and the door is shut, the car automatically locks, leaving shocked parents outside and children or pets inside," Mr Karavanas said.
"Even if you don't think your car will self-lock with the key inside, don't put yourself in the situation to find out, especially when kids are involved.
"We can't always rely on technology to work."
Tips to avoid accidental lock-ins include making a habit of always opening the windows before you put the shopping, kids or pets in the car.
Drivers could also put car keys in their pocket before putting the children in their seats, or if you don't have a pocket, the roof of the car.
The NRMA said calls about children locked in cars are put to the top of their list for help - even if callers are not members.
As well as being dangerous, leaving an unattended child locked in a car under any circumstances is illegal, with fines of up to $22,000.
Source: 9News https://www.9news.com.au/national/how-hot-it-gets-inside-cars-warning-nrma-summer/7d29b99c-7a8f-4743-9a11-c25724eb016f