What 22 degrees does to a dog left in a car in Cornwall

You only mean to be a minute. Pop into the shop, grab the thing you forgot, and the dog can wait in the car with a window cracked. It feels harmless. On a warm afternoon it can be fatal, and it happens faster than most owners would ever guess.

A car heats up faster than you think

The RSPCA puts the numbers plainly. When it is 22 degrees outside, the inside of a parked car can climb to 47 degrees within an hour. That is hot enough to cause real suffering and death.

Parking in the shade barely helps. Leaving a window open barely helps either. A car traps heat like an oven, and on a bright day in a beach car park or outside a supermarket the air inside bears no relation to how pleasant it feels when you step out.

Dogs cannot cool themselves the way we can. They do not sweat through their skin. They rely on panting, on shade, on water and on moving somewhere cooler. Shut in a car, a dog can do none of it.

The dogs most at risk

Heatstroke can affect any dog, but some struggle far sooner than others. Flat-faced breeds such as pugs, French bulldogs and boxers find breathing harder, which makes cooling down harder too. Older dogs, overweight dogs, dogs with thick coats and dogs with heart or breathing conditions are all more vulnerable.

Signs a dog is overheating

The early signs are easy to miss if you are not looking for them:

• Heavy panting and drooling
• Restlessness or agitation
• Weakness, wobbliness or staggering
• A change in gum colour
• Vomiting or diarrhoea
• Collapse or seizures in the worst cases

A dog’s body temperature climbing past 40 degrees is a medical emergency, and the damage can carry on long after the dog has cooled down.

What to do if you see a dog in a hot car

If you spot a dog in distress in a parked car, act quickly.

• Dial 999 and ask for the police. They can get there fast and they have the power to enter a locked vehicle. The RSPCA does not.
• If you are at a supermarket, shopping centre or event, ask staff to put out a tannoy call to find the owner.
• Stay with the dog and keep watching it. If its condition gets worse, be ready to call 999 again.
• You can ring the RSPCA’s 24-hour cruelty line on 0300 1234 999 for advice, but if a dog is in danger your first call should always be 999.

Before you break a window

Many people’s first instinct is to smash the glass, and the law here is not straightforward. Breaking into a car can count as criminal damage, and you may have to justify it in court. You do have a lawful excuse if you genuinely believe the owner would consent once they knew the dog was in danger. So tell the police what you intend to do, photograph or film the dog, and take the names and numbers of any witnesses before you act.

How to keep your own dog safe

The simplest protection is to leave your dog at home in a cool spot on warm days. Walk early in the morning or later in the evening when the heat has dropped. Carry water on every trip out. A frozen Kong or a lick mat will keep a dog happily occupied while you are gone.

And if a car journey on a hot day is not essential for the dog, do not make it.

The RSPCA sums the whole thing up in four words. Not long is too long.