Dogs do not sweat the way we do. They shed heat mainly by panting, and panting gets less effective as the air gets more humid. That is the whole reason a dog can be in trouble on a day that feels merely warm to you.
Heatstroke is a veterinary emergency and it can kill quickly. This article is about recognising the problem early and acting. It is not a substitute for a vet, and nothing here replaces calling one.
Early signs
These are the ones worth training yourself to notice, because this is the stage where stopping solves the problem.
- Panting that does not settle on a rest break. A hot dog that recovers after a few minutes in the shade is regulating. A dog whose panting stays heavy and fast after several minutes of rest is not keeping up.
- Thick, ropy drool. Saliva going stringy and sticky rather than thin is one of the more reliable early signals.
- Bright red gums or tongue. Compare against what your dog looks like normally, on a cool day, so you have a baseline.
- Lagging. A dog that has been out front all morning and drops behind you has told you something. Dogs will run themselves into serious trouble to keep up, especially working breeds, and they will not stop on their own.
- Seeking shade or lying down at every stop. Taken together with the above, treat it as a signal rather than laziness.
Emergency signs
At this stage you are not managing a hot dog. Get to a vet.
- Staggering, wobbling, or a loss of coordination
- Vomiting or diarrhoea, particularly with blood
- Gums going pale, grey or blue
- Glazed eyes, confusion, or unresponsiveness
- Collapse, tremors or seizure
A dog that suddenly stops panting while still clearly overheated is a bad sign, not a good one.
What to do immediately
Start cooling on the spot. Do not drive somewhere first and start cooling there.
- Stop and get into shade. Any shade. Moving generates more heat than it dissipates.
- Get water onto the thin-furred areas. Belly, groin, armpits and paw pads. That is where blood runs close to the surface. Pouring water over a thick topcoat mostly wets the coat.
- Use cool water, not ice water. Ice-cold water on a badly overheated dog can constrict the surface blood vessels and slow heat loss, and it risks sending the body into shock. Cool and steady.
- Get air moving. Evaporation is doing the work. Fanning a wet dog is more effective than more water on a still day.
- Offer small drinks. Let them drink, but do not force water into a disoriented dog.
- Call a vet. Do this even if the dog seems to recover. Heatstroke can cause internal damage that shows up hours later, and the visible recovery is not the whole picture.
Which dogs are at more risk
Every dog can overheat. Some start much closer to the edge.
Flat-faced breeds — bulldogs, pugs, boxers, French bulldogs and similar — have compromised airways, and panting is their cooling system. They are at serious risk in conditions other dogs handle easily. Dark coats absorb more radiant heat. Overweight dogs carry insulation and generate more heat moving. Puppies and senior dogs regulate less well. Thick double coats and dogs bred for cold climates struggle in heat regardless of fitness.
A dog being fit does not protect it. A conditioned working dog will simply keep going for longer while overheating.
Humidity is the variable people miss
Panting cools by evaporating moisture off the tongue and airways. In humid air, less evaporates, so the cooling system loses much of its capacity.
That is why a humid morning in the high seventies can be more dangerous than a dry afternoon in the nineties. Check humidity alongside temperature before you decide a hike is fine.
Prevention
Hike early or late and skip the middle of the day entirely in summer. Test the ground with the back of your hand for several seconds — if you cannot hold it there, it will burn paws. Carry more water than you think you need, and a bowl, and offer it often rather than all at once.
Evaporative cooling vests genuinely help by giving the dog a large wet surface for airflow to work on. They also have a real limit: they work by evaporation, so they need dry air and regular re-wetting, and in high humidity they do very little. A cooling vest is not permission to hike a dog in conditions you would otherwise avoid.
The most useful thing you can do is turn back early. There is no version of this where pushing on was worth it.
Cooling vests, collapsible bowls and trail gear are in Tactical & Trail, and the Field Guide has more on hiking in heat.