Heat in a car: six rules that are not up for negotiation

Of every subject on this site, heat inside a vehicle is the one where the gap between what people believe and what actually happens is widest, and where the mistake cannot be undone. This guide offers nothing to weigh up: there are rules.

1. Duration is not the criterion, the starting temperature is

“Five minutes” means nothing. In a vehicle parked in the sun, the cabin gains most of its heat in the first few minutes, not at a steady rate.

The only safe reasoning is binary: in hot weather, you do not leave an animal in a vehicle. Not “not for long” — not at all.

2. Windows left ajar change almost nothing

It is the token gesture that eases the conscience, and its effect is negligible. A few centimetres of opening create no air circulation at all in a stationary vehicle.

The prevention campaigns published on this subject all press this exact point, because it is the justification put forward most often.

3. Shade moves

A space in the shade at 2pm is in full sun at 3pm. It is a mistake in reasoning more than carelessness, and it accounts for a share of the accidents.

Parking in the shade does not turn a rule into an exception: it stays a rule.

4. A dog does not sweat

It regulates by panting and through its paw pads, which is far less efficient and depends on the surrounding air. In a saturated cabin, panting no longer cools anything.

Flat-faced dogs, overweight dogs, older dogs and thick-coated dogs reach that point far sooner — sometimes at temperatures that feel bearable.

5. In a camper, insulation counts for more than air conditioning

A motorhome or a van carrying an animal poses the problem differently: the vehicle is still being lived in, sometimes while parked, and the power available is limited.

The order of priorities is counter-intuitive: insulate first, ventilate second, run the air conditioning last. Insulation for windows and roof vents cuts the solar gain at source, where air conditioning fights it by drawing power; on a long stop with no hook-up, that difference is decisive.

6. What to do in case of heatstroke, in order

Get the animal out, move it into the shade, cool it gradually with tepid water starting at the legs and the belly — never with iced water, which causes vasoconstriction and makes things worse — then call a vet without waiting for any improvement.

An animal that seems better after cooling still has to be seen: the complications of heatstroke often appear several hours later.