Start with the figure everything else follows from. According to the AVMA, the interior of a parked vehicle can rise about 20 degrees Fahrenheit in ten minutes, almost 30 degrees in twenty, and more than 40 degrees within an hour. On a 70-degree day that is over 110 degrees inside the car. Cracking the windows makes no measurable difference, and parking in the shade is not a solution either.
That is the parked-car rule and it has no exceptions worth arguing about: the dog comes with you or the dog stays home. Everything below is about the other 95% of the problem - keeping a dog comfortable in a car that is actually moving, on a day that is actually hot.
Dogs cool differently, and worse than you
You sweat. A dog pants, moving air across wet tissue to shed heat by evaporation, plus a small amount through the paw pads. That system works well in dry moving air and badly in a hot, still, humid car. It also degrades sharply with age, weight, thick coats, and short muzzles - which is why the same drive that a lean young collie finds fine can genuinely endanger a bulldog. If your dog is brachycephalic, read the snub-nosed guide too, because the physiology is the same problem in a different setting.
The five things that actually work while driving
- Cool the car before the dog gets in. Run the air conditioning for a few minutes with the doors open. Loading a dog into a car that has been sitting in a car park since noon starts the trip in a deficit it may not recover from.
- Get the cold air to the back. Most cars cool the front footwells and nothing else. Point the rear vents at the dog, use recirculation, and if your car has no rear vents, angle a front one backwards. A dog in a cargo area with the seats up is in the hottest part of the vehicle.
- Shade the glass.A window shade or sunshade on the dog's side does more than any gadget. Direct sun through a rear window on a stationary dog is radiant heat with nowhere to go.
- Give it something cool to lie on. A pressure-activated cooling mat works for exactly this situation - a dog lying still on a surface for hours - and unlike a wet vest it does not leave you with a damp dog and a damp seat. Our cooling mat roundup ranks them.
- Water at every stop, in small amounts. Not one bowl left sloshing in the back. See hydration on the move.
What does not work
Cracked windows on a parked car, as above. Ice water in large quantities, which can cause a dog to gulp and vomit - cool water, offered often, is better than freezing water offered once. A fan blowing hot air, which just moves hot air. And a soaked towel laid over a dog, which restricts evaporation from the coat rather than helping it; a damp towel under a dog is the useful version.
Heatstroke: the signs, in the order they appear
Know these well enough to spot them from the driver's seat in a mirror.
- Heavy, fast panting that does not slow down when the car cools, and drooling that is thicker than usual.
- Restlessness - a dog that keeps standing up, repositioning, and cannot settle.
- Bright red or, later, dark or dusky gums; a dry, tacky mouth.
- Wobbliness, vomiting or diarrhea, confusion, collapse. This is an emergency, not a wait-and-see.
If you see the early signs: pull over somewhere shaded, get the dog out of the car, offer small amounts of cool water, and wet the paws, belly and groin with cool - not ice cold - water while air moves over the dog. Then call a vet. Heatstroke can do organ damage that is not visible at the roadside, and a dog that looks recovered still needs to be seen.
Planning a hot-weather drive
- Drive early or late. The hours either side of dawn are the whole solution to a summer road trip and they cost nothing.
- Plan stops around shade, not around fuel. A shaded verge at a quiet exit beats a sunlit service station forecourt every time. The stopping rhythm gets shorter and more frequent in heat.
- Never leave the dog while you go in somewhere,including for "just five minutes". In a number of states this is also an offense - our state law reference covers where.
- Check the asphalt before you walk. Hot pavement burns pads, and it is usually far hotter than the air. The back-of-the-hand test and the fix are in protecting paws on hot pavement.
- Take the cooling gear you would take on a hike. A cooling vest earns its place at the stops - walking a dog in one at 2pm is much easier than walking a dog without.
Crates and cargo areas in summer
A crate is the safest place for a lot of dogs in a car, and it is also the hottest. Airflow through a crate is worse than airflow around a loose dog, and a soft crate is worse than a wire one. In hot weather: wire or a well-ventilated hard crate rather than fabric, positioned where the air conditioning reaches it, never in direct sun, and never in a cargo area with a closed tonneau cover. If your dog rides in a crate, read how to secure it for the safety half of the same decision.
The rule that covers everything else
If you would not sit in that car, with the engine off, for as long as you are about to leave your dog in it - do not leave your dog in it. That single test replaces every judgment call people get wrong on a hot day, including the ones that end with a broken window and a vet bill.
