Every summer, vets see a spike in heatstroke cases, and cars are one of the main culprits. Most owners know never to leave a dog in a parked car. Fewer realise that a moving car can be a problem too, because the place the dog usually travels, the boot, is the last place your air conditioning reaches.
Here is what is actually going on back there, and what to do about it.
Why the boot runs hotter than you think
Three things work against a dog in the boot.
First, air conditioning is designed around the front seats. By the time cooled air has worked its way past two rows of seats, its effect in the boot is marginal, and with a parcel shelf fitted it is close to zero.
Second, glass. The rear screen and rear quarter windows turn the boot into the sunny end of a greenhouse. When it is 22°C outside, the inside of a car can reach 47°C within an hour. A moving car with good airflow will not hit those numbers, but a car crawling in holiday traffic with the sun on the tailgate gets uncomfortably close.
Third, the dog itself. Dogs run around two degrees warmer than we do and cannot sweat the way we can; panting is most of what they have. A dog whose body temperature passes about 40°C is heading into life-threatening heatstroke. They start every journey closer to the danger line than you do.
The setup: get the airflow right before you set off
Remove the parcel shelf. Always, in any weather. It blocks the only meaningful air path to the boot.
Cool the car before the dog gets in. Run the air con for a few minutes with the doors open. A dog loaded into a hot car starts the journey stressed and warm, and a stressed dog runs hotter still.
Point the vents up and back. Angle the dash vents towards the ceiling so cooled air rolls over the seats towards the rear. If your car has rear vents, open them fully.
Choose a ventilated cage. This is where cage design earns its money. A transit cage with proper ventilation on multiple faces lets air move through the dog's space rather than around it. It is one of the core things we design for in every Dog Box UK cage.
Add moving air: the cage fan
Still air at 25°C feels very different to moving air at 25°C, for dogs as much as people. A 12V cage fan mounted to the cage front keeps air moving across the dog for the whole journey, powered from the vehicle's 12V socket. On a hot day in slow traffic, it is the difference between a panting dog and a sleeping one.
We build our own dog cage fan unit for exactly this job. It mounts to the cage, runs off a 12V lead, and moves air where the air con cannot reach. If you regularly travel in summer, or you run a van where the load space has no vents at all, it is the single most effective upgrade you can make.
On the journey
Travel early or late. In a heatwave, the coolest windows are early morning and evening. Midday motorway traffic is the worst combination going.
Water on tap. A non-spill travel bowl in the cage, topped up at every stop. Dogs dehydrate faster than passengers on long trips.
Shade the glass. Window shades on the rear screen and quarter windows cut the greenhouse effect dramatically. Cheap, effective, no downside.
Cooling mat in the cage. Gives the dog a cold surface to choose. Most dogs find it themselves within minutes.
Stop and check. On journeys over a couple of hours, plan stops in shade. Heavy panting, drooling and restlessness are your early warnings; act on them rather than pressing on.
Never leave the dog in the parked car. Not for a coffee, not in the shade, not with the windows cracked. This one is absolute.
Know the heatstroke signs
Excessive panting, thick drool, bright red gums, unsteadiness, vomiting. If you see these, stop, move the dog somewhere cool and shaded, wet their coat with cool (not freezing) water, offer small drinks, and get to a vet urgently with the air con running on the way. Heatstroke kills dogs every British summer, and speed of response decides the outcome.
Quick answers
Does air conditioning reach the boot? Barely, and not at all with a parcel shelf fitted. Remove the shelf and consider a 12V cage fan for hot weather.
How hot does a car boot get? A parked car can go from 22°C outside to over 45°C inside within an hour. Moving cars fare better but slow traffic in direct sun still cooks the rear of the vehicle.
Is it safe to travel with my dog in a heatwave? If the journey is essential: travel early or late, ventilate properly, carry water, plan shaded stops. If it is not essential, leave the dog at home in the cool.
What temperature is dangerous for dogs? Trouble can start above 20°C for flat-faced, overweight or heavy-coated dogs. A body temperature over roughly 40°C is an emergency.
The Dog Box UK cage fan unit fits our cages and most others, and ships with a 12V power lead. Designed and built in Devon, like everything else we make.