Dogs at Higher Risk of Heatstroke

Some dogs handle heat better than others. A fit Labrador and a French Bulldog aren't playing in the same league when the temperature rises, and the difference comes down to how they're built on the inside. Flat-faced breeds, overweight dogs, and dogs with very dark coats carry a real disadvantage when it comes to heatstroke.

Which dogs suffer heatstroke

Here we go over these profiles and why summer poses a risk for them that shouldn't be underestimated.

When a dog's body loses the ability to get rid of the heat it produces, its temperature climbs above 41°C and the animal enters a genuine medical emergency. Veterinary medicine calls this non-febrile hyperthermia from thermoregulatory failure. It can kill within minutes. And the risk isn't spread equally across all dogs.

The most common triggers are extreme ambient heat and intense exercise under thermal stress, as detailed in "Pathophysiology of heatstroke in dogs – revisited" (2017). But the animal's body shape and health status determine how soon this mechanism collapses.

Brachycephalic breeds are first in line for vulnerability. The French Bulldog, English Bulldog, Pug, and Boxer carry respiratory anatomy that works against them from the start. Narrow nostrils from stenotic nares, an oversized soft palate, and often a narrower-than-normal trachea. This combination is what veterinarians call BOAS (brachycephalic obstructive airway syndrome), and it turns panting — a dog's main cooling mechanism — into something inefficient and labored. When the heat closes in, the system fails sooner.

Very old dogs and puppies just a few months old are also at-risk groups, along with any animal carrying heart, respiratory, or endocrine conditions like hypothyroidism. Their capacity to respond to thermal stress is already reduced, which makes multi-system failure appear much faster.

The causes of heatstroke

The main cause of heatstroke is the dog's body being unable to release excess accumulated heat, exceeding its capacity to compensate. This can be triggered through two main pathways: environmental and exercise-related.

The environmental cause is the most obvious: leaving a dog in an enclosed, poorly ventilated space that heats up quickly, like a car parked in the sun. On a 24°C day, a vehicle's interior temperature can exceed 40°C in under 30 minutes, creating a deadly trap. But this also includes spaces like shadeless terraces, carriers in a car trunk, or rooms with poor air circulation.

The second cause, often underestimated, is strenuous exercise in hot or highly humid conditions. A long walk at midday in summer, an intense play session where dogs suddenly run around like crazy, or practicing sports like canicross without proper hydration and acclimatization beforehand can all be the trigger. The muscular effort itself generates a large amount of internal heat that, combined with ambient heat, overwhelms the animal's cooling mechanisms.

Overlooked risk factors: dark coat, double coat, and obesity

Beyond brachycephalic breeds, there are other less well-known but equally significant risk factors. Coat color is one of them. A dark coat, such as black, dark brown, or dark gray, absorbs more solar radiation compared to lighter coats. This means that, under the same sun, a Black Labrador will heat up significantly faster than a Yellow Labrador, increasing their thermal load from the very start.

Obesity is another critical and very common factor. Excess body fat acts as an effective thermal insulator, preventing internal heat from dissipating outward. Also, overweight dogs usually have lower exercise tolerance, tire more quickly, and are therefore more prone to overexertion. A dog weighing more than the ideal weight for their breed and build usually carries an increased risk.

Contrary to popular intuition, double-coated breeds (like the German Shepherd, Siberian Husky, or Samoyed) also face a unique challenge. Their dense, woolly undercoat is designed to trap air and insulate them from cold, but in summer that same layer can make it harder for body heat to escape. The key isn't shaving them, since that can irreversibly damage their coat and expose their skin to sunburn, but rather keeping up thorough, frequent brushing to remove dead undercoat and allow better skin ventilation. Identifying heatstroke requires watching for a combination of signs: excessive, loud panting, dark red or bright gums, thick saliva, weakness and stumbling, and in advanced stages, vomiting, bloody diarrhea, and even loss of consciousness.

How to spot heatstroke before it's too late

Once heatstroke starts, the window to react is very narrow. Symptoms escalate within minutes. That's why you need to know what to look for and not wait until it's obvious.

The first warning sign is usually panting that doesn't match the situation — continuous, loud, that doesn't ease up even when the dog is lying down somewhere cool. The body has been trying to lower its temperature for a while and isn't succeeding. Then changes in the mouth appear. Gums, which normally show a uniform pink, turn bright red; if they already show a bluish or purplish tone, the animal has gone a while without proper oxygenation. The mouth fills with thick, sticky saliva. Some dogs won't stop pacing in circles; others just stop and refuse to move. Leg tremors usually accompany all this.

If nothing is done, the decline speeds up. The legs stop responding properly, the dog stumbles, falls. Diarrhea appears, along with vomiting, often bloody. Disorientation becomes evident — they stop responding, their gaze loses focus — and from there to collapse and seizures there's not much distance left. At that speed, the damage building up in the kidneys, liver, and brain is often irreversible. Without urgent veterinary care, mortality at this stage is extremely high.

The hours between 12:00 and 18:00 are off-limits for intense activity. Walks early in the morning or in the late afternoon, looking for shaded areas and, if possible, dirt or grass surfaces. Asphalt holds onto heat for hours and burns paw pads before you even notice.

How to prevent heatstroke

Fresh water always available. At home and out on the street. A portable bottle with a foldable bowl weighs very little and can make all the difference on a summer walk. If your dog is one who doesn't drink much, a few ice cubes in the bowl or a piece of seedless watermelon usually gets them interested. Careful with this: once heatstroke is already underway, forcing your dog to drink water or giving them medication is a mistake. The priority is to physically cool the animal down and get to the vet as soon as possible.

Indoors, the coolest room in the house is their spot. Cross-ventilation, air conditioning if you have it, and the water bowl always within reach. Gel mats or damp towels work well — they lie down on top and cool off without you needing to cover them. For breeds or dogs at higher risk, cooling vests soaked in cold water are a practical option for short outings when the heat really presses in.

Preparing the environment for heat-sensitive dogs

The first step is to survey your home. Breeds prone to heatstroke need a clear place to take shelter, and that depends on what you set up. Tile floors and rooms away from sun-facing windows are the starting point — that's where the cool beds and cooling mats go, spread across several spots so the dog doesn't have to search for them. With blackout curtains during the sunniest hours, you can lower that room's temperature by up to five degrees without touching the thermostat.

Air conditioning helps, but just turning it on isn't enough. A floor fan set low improves air circulation a lot, and if you place a frozen water bottle in front of it, the air reaching the dog comes out several degrees cooler. That said, don't point it directly at the animal — the idea is for the airflow to surround their resting area, to circulate, not hit them head-on. And if you live somewhere humid, skip the humidifier — it makes evaporation from panting harder and works against the mechanism the dog uses to regulate their own temperature.

For the most critical times of day, it's worth having something ready beforehand. A damp towel soaked in cold water — cold, not icy — laid out in the hallway can serve as an improvised thermal refuge. Frozen water bottles or empty milk cartons work well wrapped in a thin pillowcase — the dog can rest their body against them or simply stay nearby. What you should never do is apply ice directly to the skin or use commercial cooling products without constant supervision.

Feeding times also come into play. In summer it makes sense to give kibble at night, once it cools down, moistening it with a bit of unsalted, onion-free chicken broth that you've chilled in the fridge beforehand. For water, automatic dispensers with a reservoir ensure there's always something fresh available. Adding ice cubes made from diluted broth, or small apple pieces, to the water bowl usually encourages dogs who don't drink much.

Walks during the hottest hours need to be rescheduled, no excuses. Meanwhile, the dog still needs to go out. If you have a terrace or balcony, artificial grass protected with a translucent tarp works well for those urgent moments. For dogs who refuse to use artificial surfaces, a large tray of soil placed under cover can be the most practical solution.

The car deserves a special mention. A vehicle parked in the shade at nine in the morning can turn into an oven by midday, even if it doesn't look like it from outside. Windshield sunshades, leaving the windows cracked open a couple of centimeters with some kind of security system, and never leaving the animal inside without active ventilation are basic measures. It doesn't matter if it's ten minutes or twenty.

Dogs at risk of heatstroke sense heat before we do. Learn to read when yours starts seeking out cool surfaces or moves around more restlessly than usual. These signs show up before the problem becomes visible, and they're the cue to start environmental cooling measures without waiting for the situation to get worse.

Urgent first aid: the 30-minute rule

Thirty minutes. That's the window a dog with heatstroke has before the damage starts becoming irreversible. Acting well within that time — and doing it with a clear head — can completely change the outcome. The first step is to get the animal away from wherever they overheated and move them somewhere shaded, cool, with some air circulation.

To cool the dog down, use cool water, never ice-cold. With very cold water, the opposite of what you want happens. The surface blood vessels constrict and the heat stays trapped inside the body instead of escaping. Thoroughly wet the head, neck, armpits, and groin area, where blood vessels are closer to the skin. Then place a fan in front of the animal. Evaporation is what actually brings body temperature down.

While applying the cooling measures, call an emergency vet clinic to let them know you're on your way. Don't try to normalize the temperature at home. Start this process and be at the clinic in under thirty minutes. Drive there with the windows down or the AC on full blast. Once there, they'll be able to precisely control internal temperature and treat the systemic complications that arise when the body overheats for too long — those are the ones that truly put the animal's life at risk.

An owner who knows how to act in those first few minutes greatly improves their dog's chances of pulling through.

Knowing which breeds or physical conditions raise the risk helps you get ahead of it, but in extreme heat any dog can collapse. What really makes a difference in practice is learning to recognize the signs while there's still time to react — very intense panting, thick drool, bright red gums — and already having a plan for what you'll do if it happens. Fresh water on hand, shade, wetting the animal down without resorting to ice. At the slightest suspicion, get to the vet without delay. In these cases, every minute that passes counts against you.