France recorded its hottest day on record on Wednesday, with a national average temperature of 29.9°C, prompting Météo-France to place 72 départements under red heatwave alert and a further 17 under orange, covering more than 95% of the population — and renewing urgent warnings from health and safety authorities over the dangers of leaving children, pets or vulnerable people inside parked cars, even for a few minutes.
The Ministry of the Interior warns that with an outside temperature of just 26°C, ten minutes is enough for a young child to die inside a parked car. The mechanism is straightforward: sunlight passes through the windscreen and windows, heats the dashboard and seats, and that heat becomes trapped inside the cabin. According to a Stanford University study published in the journal Pediatrics, a car’s interior temperature rises by an average of 80% during the first ten minutes of exposure, and the rate of increase does not slow down — it accelerates as time passes.
On a day when it is 35°C outside, a car’s interior can reach 45°C in just ten minutes, and exceed 50°C within twenty. In extreme cases, after an hour, interior temperatures can pass 70°C, with the dashboard regularly reaching 90°C.
Why children are at far greater risk than adults
A child’s body heats up three to five times faster than an adult’s, according to the American Academy of Pediatrics, because their body surface is proportionally larger and their temperature-regulation system is still immature. Once trapped in a hot car, infants and young children can become severely dehydrated and develop hyperthermia within minutes, with symptoms including mental confusion, dizziness and, in severe cases, convulsions or loss of consciousness. A heat stroke episode in these conditions can be fatal or cause lasting damage if a child is exposed for too long. Crucially, a child secured in a car seat has no way to free themselves, open a door or signal for help from outside the vehicle.
Common precautions offer little real protection
Several widely held assumptions about reducing the risk do not hold up under the physics involved. A black car reaches its maximum interior temperature only five to eight minutes faster than a white one, and after 30 minutes the difference between the two is just two to three degrees. Leaving a window slightly open makes almost no difference to how quickly the cabin heats up. Parking in the shade helps, typically lowering the interior temperature by five to eight degrees, but shade moves with the sun, and even a shaded car can exceed 40°C during extreme heat.
The same danger applies to pets
Veterinary and road safety authorities apply the same warning to animals as to children. If the weather is hot, neither a child nor an animal should be left alone in a car, since within roughly 15 minutes a vehicle left in full sun can reach an interior temperature that threatens the life of its occupants. A dog suffering heat stroke in these conditions can die within 15 minutes.
What to do if you see a child or animal alone in a hot car
Anyone who sees a child left alone in a vehicle, with no parent nearby, should not wait more than a few minutes before calling the emergency services on 18 (fire brigade), 15 (SAMU) or 114 (the emergency number for the deaf and hard of hearing). French law protects anyone who breaks a car window to remove a child or animal showing signs of heat stroke, under Article 122-7 of the Penal Code, which exempts from criminal liability a person who takes necessary action to protect themselves, another person, or property from an immediate or imminent danger.
The advice from every authority cited is the same and admits no exceptions: never leave a child, an animal or a vulnerable person inside a stationary vehicle, even briefly, even in the shade, and even with a window cracked open.
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Photo credit: Alexander Grey, Unsplash