Heatstroke in Dogs and Cats: What to Notice and Who to Call

Published by Paw Multiverse (A.I.T. Multiverse Consulting Ltd) · Last updated 4 August 2026

Heat emergencies rarely announce themselves. They usually start as a small wrongness on an ordinary afternoon: a dog who lies down on a walk they have done a hundred times, a cat who has gone very quiet in a conservatory, a pet who came in from the garden and has not settled. Nothing is obviously wrong yet, so you do the human thing and wait a minute to see.

That minute is the part worth talking about, and it is the reason this page exists in the shape it does. Heat illness is one of the few situations where the gap between "probably fine" and "in serious trouble" is measured in minutes rather than hours, and where the owner's instinct to handle it themselves is strongest, because it feels like a problem with an obvious answer. It is not a problem with an obvious answer. What follows is about recognising, recording and reporting - the three things you can do well from where you are standing.

Why heat illness is not a problem you can solve from a web page

Dogs and cats do not sweat the way we do. They shed heat mainly by moving air over wet surfaces - panting, and to a much smaller extent through their paws. That system works well in dry, moving, cooler air and badly in still, humid, hot air. It is also a system that can be overwhelmed, and once it is overwhelmed, the animal's own temperature regulation stops helping and starts working against them.

The reason that matters to you, right now, is that the damage in a heat emergency is not only the heat. It is what the heat does to the gut lining, to clotting, to the kidneys and to the brain, and much of that unfolds over the hours after the animal looks better. Which means two things. First, an animal who appears to improve has not been shown to be safe. Second, the correct sequence of what to do, how fast, and when to stop is a clinical judgement made on a specific animal by a person who is trained to make it - not a set of steps that can be safely printed for every dog, every cat, every situation.

Getting that sequence wrong is not a neutral outcome. Interventions that sound sensible can drive an animal into a worse state, mask the signs the vet needs to see, or eat the minutes that were the actual treatment. This site used to carry step-by-step instructions on this page. It does not any more, deliberately, and the reasoning is set out in full on Pet First Aid Truths - What Not To Do and Why.

What you are actually looking at - describing, not diagnosing

The single most useful skill in the first two minutes is being able to say what you can see in plain, concrete language. Vets triage by description over the phone constantly. They are not expecting you to know what is wrong; they are expecting you to be a good camera. Describe, do not interpret.

Useful things to look at and be able to report:

• The breathing. Not just "panting" - is it fast, noisy, open-mouthed, with the neck stretched out, with the elbows held away from the body? Has the sound changed? Can they stop panting for a moment, or not at all?
• The gums and tongue. Colour and how they look compared to normal for this animal. Say what you see, in ordinary words, rather than reaching for a medical term.
• The posture and movement. Standing, sitting, lying flat, unable to get up, wobbly, stumbling, walking into things, circling.
• Responsiveness. Do they respond to their name, to you entering the room, to a lead being picked up? Is the response slower or stranger than usual?
• Anything that has come out. Vomiting, diarrhoea, drooling, and roughly when and how much.
• Behaviour that is out of character. A cat hiding somewhere they never hide. A dog who will not lie down, or who cannot get comfortable, or who is suddenly clingy or suddenly absent.

Resist the urge to translate what you see into a conclusion. "He is panting hard, his gums look darker than usual and he has not got up in four minutes" is far more useful than "I think he has heatstroke". The first can be acted on. The second has to be unpicked before it can be acted on.

The things only you can tell them

A vet who has never met your pet is missing the one dataset you own completely: the baseline. You are the only person who knows what normal looks like for this animal, and the deviation from normal is often the most informative thing in the whole call.

• What this pet is like on an ordinary warm day - how much they usually pant, how quickly they normally settle after exertion.
• What changed, and when you first noticed the change.
• Whether this has happened before, and what happened then.
• Anything currently different about them - recent illness, a new medicine, a recent procedure, pregnancy or nursing, a known heart or airway problem.

If your pet has a condition or takes anything regularly, read it off the packet rather than from memory. Names are easy to half-remember and hard to guess at from a partial description.

The facts to gather while the phone is ringing

Gathering is something you can do with your hands and eyes while the call connects. It never replaces the call and it is never a reason to delay it. Our two-minute preparation for calling the vet covers this in full; the heat-specific version is short.

• Where the pet has been. Indoors, outdoors, in a car, in a conservatory or utility room, in a run, in a crate, in a garden with or without shade.
• For how long, in clock times. "Out from about two until quarter past three" is more reliable than "about an hour" - elapsed times drift under stress, clock times do not.
• What the conditions were. Sun or shade, still or breezy, humid, hard ground, a closed room, a vehicle.
• What they were doing. Resting, walking, running, playing, being transported, being groomed, being left.
• Who the pet is. Species, breed or best guess, age, rough weight, whether they are flat-faced, overweight, thick-coated, very young or elderly.
• Whether they had access to anything else. Heat and a swallowed substance can arrive on the same afternoon; if there is any chance something was eaten, say so, and see My Dog Ate Something - What To Do, Step by Step.

If your pet's weight is a guess, say it is a guess and give a range. A range you are honest about is more useful than a confident number that is wrong. If you want a rough figure to work from on a calm day, the ideal weight calculator is there for that, not for an emergency.

Making the call - how to say it when they pick up

The person answering is triaging. Give them the shape of the problem in the first sentence and the detail afterwards. Something like: "My dog has been outside in the heat for about an hour, he came in twenty minutes ago and he is panting hard and cannot settle. He is a nine-year-old Labrador, roughly thirty kilos. I am fifteen minutes away."

Then let them ask. Write down what they tell you, and read it back before you hang up - under stress people reliably mishear one detail out of three. Two questions worth asking before the call ends: what should I watch for on the way, and what would make you want to see him sooner. If they give you anything to do, do that, not what a web page said.

Tell them you are coming. A practice that knows an overheating animal is fifteen minutes out can have staff and space ready, and that preparation is worth more than anything you could improvise on the journey.

Why this page does not tell you what to do to your pet

This is the section people skip to, so it is worth saying plainly. We are not withholding a simple trick. There are things that can be done for an overheating animal, and a vet on the phone may tell you to do some of them - scaled to that animal, that situation and how far away you are. Written down for everyone, the same actions become dangerous, because the judgement that makes them safe is the part that cannot be printed.

Three specific failure modes, none hypothetical:

• Overcorrection. Doing something too fast, too far or for too long can cause its own harm. Knowing when to stop is as clinical as knowing when to start, and a page cannot see your animal.
• Substitution. An owner busy performing a procedure is an owner who is not driving to the vet. The most common serious mistake in a heat emergency is that everything happened except the journey.
• Wrong animal, wrong situation. Advice written for a healthy adult dog can be actively harmful for a flat-faced breed, a cat, a very old or very young animal, one with a heart or airway condition, or one whose problem is not actually heat.

What we will say, because they are refusals rather than techniques: do not give anything by mouth unless a vet has told you to; do not reach for anything from a human medicine cabinet; do not act on advice written for a different species; and do not decide to wait and see whether it improves. The full version of that reasoning is on Pet First Aid Truths.

Why "he seems better now" is not the end of it

This is the most important paragraph on the page. Animals in heat trouble often do look better after a while, and that improvement is real but only skin-deep. The processes that cause the serious outcomes - the gut, the clotting, the kidneys - are largely invisible from the outside and can declare themselves long after the animal has apparently recovered and gone to sleep in their bed.

So an improvement is a reason to feel relieved on the way to the vet, not a reason to cancel the trip. If you have already spoken to someone and they asked to see your pet, go, even if the animal walking to the car looks like the animal from yesterday. And if you did not call because things got better on their own, call anyway and describe what happened; let them decide whether it needs a look.

Which pets are least able to cope

Not a diagnostic checklist - any animal can get into trouble in the heat - but risk is not evenly distributed, and knowing where your pet sits changes how early you should be picking up the phone.

• Flat-faced breeds. The cooling system is airflow over wet surfaces, and a shortened airway makes moving that air harder work, which itself generates heat.
• Thick or double coats. Insulation works in both directions.
• Overweight animals. More heat produced, more insulation, less efficient breathing.
• The very young and the very old. Less reserve, and less ability to remove themselves from a hot place.
• Animals with heart, lung or airway conditions, and those on medicines - mention every one of them by the name on the packet.
• Animals who cannot leave. A pet in a car, a crate, a run, a conservatory or a garden with no shade has no option to self-rescue, which is why those situations dominate the serious cases.

On a calm day - the part that actually prevents this

Almost everything that works here is prevention, and prevention is the one area where an ordinary owner outperforms an emergency vet.

• Never leave a pet in a parked vehicle, for any length of time, in any weather you would describe as warm. There is no version of this that is fine.
• Move walks to the coolest parts of the day. If you want a sanity check before you head out, we built Is it too hot to walk my dog? and the broader walk planner for that decision - use them to talk yourself out of a walk, not into one.
• Make sure there is shade that stays shade as the sun moves, and water in more than one place.
• Watch how much your pet is drinking in warm spells; a change is information. The water intake calculator gives you a reference point for ordinary days.
• Learn what your own animal looks like when they are working hard but coping, so that "not coping" is obvious to you. Reading your pet's body language is the slow version of this skill.
• Put your vet's number and your nearest out-of-hours number somewhere you can find them in ten seconds. The printable emergency pack exists for that.

Where this page sits

This is one of four situation pages that share the same approach - notice, record, prepare, call. The others are choking, bleeding and wounds and seizures. The reasoning behind all of them is on Pet First Aid Truths, the phone-call preparation is on Before You Call the Vet, and if something was swallowed, start at My Dog Ate Something. For the wider "is this an emergency" question there is the emergency triage helper and the pet emergency hub, and for finding somewhere open, the emergency vet finder.