Heatstroke in Dogs and Cats: Risks and First Aid
Heatstroke is a veterinary emergency that occurs when a pet's body temperature dangerously rises due to extreme environmental heat, intense physical exertion, or both.
PETS
9/29/20256 min read
Heatstroke is a veterinary emergency that occurs when a pet's body temperature dangerously rises due to extreme environmental heat, intense physical exertion, or both. In dogs and cats, the normal temperature is around 38–39 °C (100.4–102.2 °F); if it exceeds 41–42 °C (105.8–107.6 °F), the body enters extreme hyperthermia, risking multi-organ failure and death within minutes (1, 2). Unlike humans, dogs and cats cannot sweat over their entire skin; they rely on panting and contact with cool surfaces to dissipate heat (1, 3). When these mechanisms fail, a severe metabolic imbalance occurs, which can cause brain damage, kidney failure, circulatory collapse, and coagulopathies (1, 4). That’s why it's crucial to recognize the symptoms and act quickly.
What is Heatstroke and How Does it Occur?
Heatstroke is essentially an abnormal increase in the animal's internal temperature. It happens when the body generates or absorbs more heat than it can get rid of. This can occur due to extreme environmental heat and high humidity (when the air cannot absorb heat through evaporation) or excessive exercise on a warm day (1, 5). For example, a dog running non-stop in a sunny park or a cat locked in a car under the sun can accumulate heat very quickly. Due to extreme heat, cellular processes are altered, organs become inflamed, and the animal suffers a kind of internal "self-destruction," leading to the rapid failure of the heart, lungs, kidneys, and brain (1, 2). In veterinary practice, a temperature exceeding 40–42 °C (104–107.6 °F) is considered heatstroke (2, 6).
Risk Factors
Certain factors increase the likelihood of heatstroke in dogs and cats. The main factor is intense environmental heat, especially if accompanied by high humidity and lack of ventilation, which prevents the air from absorbing heat from the animal's body (5, 7). Enclosed spaces without shade or air circulation (e.g., a car or a room without AC) severely raise the risk; in fact, the interior of a vehicle can reach 50 °C (122 °F) in just a few minutes under the sun (7, 8). Prolonged or vigorous physical exercise under these conditions (running, playing non-stop) can precipitate hyperthermia even in healthy dogs (9, 10).
Additionally, there are intrinsic factors that predispose pets:
Brachycephalic breeds (flat-faced) like Pugs, Bulldogs, or Persian cats have narrow airways that impede effective panting (11, 12).
Obesity and fat deposits also insulate heat and worsen cooling (10, 12).
Very young or senior animals lack efficient thermal regulation mechanisms.
Pre-existing respiratory, cardiac, or neurological diseases increase vulnerability to heat (12, 13).
In summary, an elderly, overweight dog with a very short muzzle, jogging under the midday sun, combines several of these risks simultaneously.
Early and Advanced Clinical Signs
Early signs are usually physical and behavioral. One of the first symptoms is excessive panting (open-mouth breathing) along with profuse drooling and very red gums (14, 15). The dog or cat may appear restless, agitated, or confused. Persistent and intense panting indicates the animal is struggling to ventilate heat (14, 15). Tachycardia (accelerated heart rate) and reddened mucous membranes (very red gums and tongue) are also common. When touched, the coat is often very hot and dry.
If the condition progresses unchecked, more severe symptoms appear: the animal loses strength and coordination. They may become lethargic, trembly, and show loss of balance or ataxia (16, 17). Vomiting and diarrhea (sometimes bloody) are frequent due to thermal stress on the body. In critical stages, circulatory collapse can occur, with extreme weakness and sudden falling. Worrying neurological signs may also appear: seizures, disorientation, or coma. The latter reflect brain injury and are associated with a high risk of death (14, 18).
It's important to note that some symptoms may vary between dogs and cats. For example, disoriented pets may stagger or have seizures as the heatstroke worsens (14, 19). Immediate action must be taken at the first sign of these symptoms.
Differences Between Dogs and Cats
Although both can suffer from hyperthermia, it manifests differently. Dogs typically pant vigorously and show their discomfort with agitation or by continuing their activity (they may keep running until they collapse) (20, 21).
Conversely, cats pant much less and often respond to heat by seeking a cool, quiet place; they may start compulsively licking themselves to cool down, as their main way to dissipate heat is through mild panting and grooming (22). This difference makes feline heatstroke sometimes "silent": an overheated cat usually stays still, hides, or suddenly lies down.
Mucous membrane color also varies: in dogs, heatstroke causes pale gums that may later turn red upon improvement, while in cats, abnormally dark or intense red tones may be observed (23). Another point: certain cat breeds (flat-faced, like Persians or Siamese) are also more sensitive to heat due to an anatomy similar to brachycephalic dogs (24). In summary, dog owners will notice respiratory acceleration and an inability to stop moving sooner; however, with cats, it is advisable to be alert to subtle changes in behavior (unusual lethargy, excessive drooling, or vomiting), as they don't pant as much or exhibit such obvious symptoms.
What to Do Immediately (First Aid)
If heatstroke is suspected, the first step is to gradually cool the animal while seeking urgent veterinary care (25, 26).
Move the pet to a cool, shaded area is the priority. If outdoors, move them to the shade, opening windows or using the air conditioner if possible (25, 26).
Offer fresh water to drink in small amounts, but do not force them to swallow quickly (to avoid aspiration) (26).
Moisten their body: Apply wet cloths with lukewarm or cool water to the head, neck, chest, armpits, and abdomen, areas where the skin is most exposed (25, 27).
You can spray them with cool water (never icy) and use a fan or hand fan to encourage evaporation (25, 27).
A useful strategy is to wet the paws, ears, and groin, where blood circulation is intense, which helps dissipate heat (25, 28).
In any case, the cooling must be progressive. Avoid sudden temperature changes: cool or lukewarm water is recommended, but never icy, to prevent a reverse thermal shock (sudden hypothermia) (27). As the animal's ambient temperature drops, continue with the fan and do not cover the dog or cat with any blanket. Finally, even if you start these measures, the most important thing is to take them to the veterinarian as soon as possible to complete the treatment (29, 30).
What NOT to Do
Knowing what to avoid is as important as knowing what to do. Under no circumstances should you:
Apply ice water or wrap the animal in ice. Very abrupt changes can cause a hypotermic reaction or cardiac arrest (27, 31).
Submerge the dog or cat in cold water or use ice cubes directly on their skin (31).
Cover them with blankets or clothing, as this would retain heat instead of dissipating it.
Place the animal directly in front of a fan without water, as this can dry out their airways and worsen panting (32).
Never force the animal to drink large amounts of water suddenly: give small sips (26). If the animal is unconscious or seizing, do not try to give them anything by mouth.
The priority at all times is to stabilize them with gradual cooling and get professional help.
Prevention
Prevention is key to keeping pets safe in warm weather.
At home, ensure they always have access to clean, fresh water and access to shaded areas or air conditioning during the day (33, 34).
When going for walks, always plan outings for cooler times: early morning or late evening, avoiding the middle of the day (between 11 am and 4 pm) when the sun is strongest (34, 35).
Asphalt and concrete can reach very high temperatures and burn paw pads; walk on dirt or grass and in the shade. Carry a bottle of water to offer the pet drinks periodically.
Never leave your dog or cat alone inside a parked car, even with the windows slightly open (8). In a few minutes, the internal temperature of the vehicle rises dangerously.
Avoid excessively shaving the animal's coat during the summer (36), as the coat also protects them from the sun and acts as insulation. For breeds with very long fur, a good maintenance trim (not a total shave) may be enough.
Consider individual factors: brachycephalic dogs, puppies, seniors, and those with dark fur require extra protective measures (12, 37).
In summary, the key preventive measures are: constant water access, ventilation/AC, avoiding direct sun and intense exercise during hot hours. With these precautions, the probability of a hyperthermia emergency can be greatly reduced.
When to Go to the Veterinarian Urgently
After applying the initial cooling measures, you must always seek urgent veterinary attention. It is not enough for the pet to seemingly return to normal. Many internal organs can continue to suffer hidden damage. A professional must evaluate them as soon as possible (29, 30).
Specifically, it is considered an emergency if the animal shows severe symptoms: collapse, seizures, fainting, or bluish gums. These signs indicate serious circulatory or neurological compromise and require immediate treatment, often with intravenous fluids and monitoring at the clinic (18, 19). As a general rule, in the presence of heatstroke, do not delay the visit: every minute counts.
Sources: Information obtained from veterinary experts and reference centers on veterinary emergencies (1, 4, 5, 14, 26), detailing symptoms, pathophysiology, and prevention/first aid measures for hyperthermia in dogs and cats.
(1, 18) Urgencias Ambientales (I): Golpe de Calor – VetPraxis
https://vetpraxis.net/2014/12/12/urgencias-ambientales-i-golpe-de-calor/
(2, 3, 10, 19, 21, 22, 23, 26, 27, 28, 31) Golpe de calor en perros y gatos. Síntomas y primeros auxilios
https://eoc.cat/golpe-de-calor-perros-gatos/
(4, 12, 20, 25, 29, 32) Síntomas, consecuencias y tratamientos de los golpes de calor en perros y gatos • Veterinaria Dr. Brenes
(5, 6, 9, 11, 15, 16, 24, 33, 35, 36, 37) Golpe de calor en perros y gatos
https://hospitalveterinariopuchol.com/noticias/prevenir-golpe-calor-animal/
(7, 13, 34) Síntomas de golpe de calor en perros y cómo aliviarlos | AniCura España
(8, 14, 17, 30) Golpes de calor en mascotas: qué hacer y cómo evitarlos
https://www.kivet.com/blog/como-actuar-ante-golpes-de-calor-mascotas/
AgroPetEd
Information about animals and agricultural practices
© 2025. All rights reserved.