Heatstroke is one of the most dangerous — and most preventable — emergencies a pet can face. Unlike humans, dogs and cats cannot sweat through their skin to cool down. They rely almost entirely on panting, and when the heat load outpaces their ability to dissipate it, core body temperature climbs fast. A landmark multicenter study published in Scientific Reports analyzing more than 900,000 UK dogs found that about one in seven dogs taken to the vet for heat-related illness died from it. Cases spike sharply in warmer months, and many of the deaths occurred in otherwise healthy pets who simply got too hot during a walk, a car ride, or a day in the backyard. Understanding how heatstroke develops, who is most at risk, and what to do in the first critical minutes can save your pet's life.

How Dogs and Cats Actually Cool Down

A dog's normal body temperature sits between roughly 101 and 102.5°F (38.3–39.2°C), and a cat's is similar. Heatstroke is generally defined as a core temperature above 105.8°F (41°C) accompanied by signs of organ dysfunction, according to reviews in veterinary emergency medicine. Because pets lack functional sweat glands over most of their body — dogs have a small number in their paw pads, and cats have a few more there as well — they shed heat primarily through panting, which evaporates moisture from the tongue, mouth, and upper airways.

This cooling system works well in moderate conditions but collapses quickly when humidity is high, when airflow is limited, or when a pet cannot rest. Panting depends on evaporation, and when the air is already saturated with moisture, evaporation slows dramatically. That is why a humid 80°F day can be more dangerous than a dry 95°F day. Cats are slightly better insulated against heat than dogs thanks to their grooming behavior — saliva evaporating from the coat provides a modest cooling effect — but cats can and do develop heatstroke, particularly indoors in poorly ventilated rooms.

Who Is Most at Risk

Heatstroke can strike any pet, but certain groups are far more vulnerable. The Scientific Reports study, along with research from the Royal Veterinary College's VetCompass program, identified several consistent risk factors that every owner should understand.

Brachycephalic breeds — flat-faced dogs like English Bulldogs, French Bulldogs, Pugs, Boxers, and Cavalier King Charles Spaniels — are dramatically overrepresented in heatstroke cases. Their compressed airways and elongated soft palates make panting inefficient. Research from the Royal Veterinary College found that French Bulldogs had roughly six times the odds of heat-related illness compared to Labradors, and English Bulldogs fared even worse. Persian cats and other brachycephalic feline breeds face similar airway limitations.

Large and heavy dogs generate more metabolic heat and cool less efficiently. Golden Retrievers, Chow Chows, and giant breeds all show elevated risk in the research literature.

Obese pets carry extra insulation and struggle to offload heat. Senior pets often have underlying heart or respiratory disease that reduces their reserve. Very young puppies and kittens have immature thermoregulation. Dogs with thick double coats — Huskies, Malamutes, Bernese Mountain Dogs — were bred for cold climates and overheat easily in warm ones. Dogs with laryngeal paralysis or other airway conditions are also at markedly higher risk.

The Warning Signs

Recognizing heatstroke early matters enormously, because survival drops sharply the longer core temperature stays elevated. According to the American Veterinary Medical Association and the ASPCA, the signs to watch for include:

Cats tend to show heat distress more subtly than dogs. A cat that is panting with its mouth open is already in significant trouble — open-mouth breathing is abnormal for cats outside of extreme stress or illness. Other signs in cats include restlessness, pacing, grooming frantically, seeking cold surfaces, and lethargy. If you see a cat panting, treat it as an emergency.

The Most Dangerous Scenarios

A surprisingly large share of heatstroke cases happen in ordinary circumstances, not just on record-hot days. The Royal Veterinary College analysis found that exertional heatstroke — triggered by exercise — was the most common cause in dogs, followed by environmental heatstroke from hot weather or confinement. A brisk walk at midday, a game of fetch in the sun, or a hike on a warm trail can all push a vulnerable dog past safe limits in under an hour.

Cars are a notorious danger. Research published by the American Veterinary Medical Association shows that the interior of a car parked in 70°F weather can exceed 100°F within 20 minutes, and on an 85°F day it can reach 120°F very quickly. Cracking the windows makes almost no measurable difference. Never leave a pet in a parked car, even briefly, even in the shade.

Other high-risk situations include being left outside without shade or water, confinement in a sunroom or conservatory, hot pavement that burns paws and radiates heat back up onto the body, travel crates in direct sun, and dogs tied up in yards. Hot pavement is a particular hazard — asphalt can reach temperatures well above 125°F on a sunny 85°F day. If you cannot comfortably hold the back of your hand on the pavement for seven seconds, it is too hot for your dog's paws.

Prevention: What Actually Works

The good news is that most cases of heatstroke are preventable with a few consistent habits.

Walk during cool hours. Early morning and late evening are dramatically safer than midday. On hot or humid days, shorten walks or skip them entirely and provide indoor enrichment instead. The AVMA recommends checking both temperature and humidity — a 75°F day with 90 percent humidity can be more dangerous for a brachycephalic dog than an 85°F day with dry air.

Always provide shade and fresh water. Outdoor pets need multiple shaded spots that shift with the sun and water bowls that will not tip over or run dry. Adding ice cubes to water is fine but is not a substitute for shade.

Know your pet's limits. Brachycephalic, senior, overweight, and thick-coated pets have a narrower safety window than lean, healthy dogs in their prime. Err on the cautious side.

Acclimate gradually. Research on working dogs shows that heat tolerance improves with gradual exposure over one to two weeks. A dog that has spent winter indoors cannot safely handle the first 80°F day of spring at full intensity.

Use cooling tools wisely. Cooling mats, damp towels, fans, and shallow wading pools can all help. Avoid ice baths and ice packs for prevention — those are reserved for emergency cooling and can cause other problems if misused.

Skip the muzzle and tight collar on hot days. Panting is your pet's only effective cooling mechanism. Anything that restricts airflow through the mouth is dangerous in the heat.

What to Do if You Suspect Heatstroke

Heatstroke is a true emergency. According to guidance from the American College of Veterinary Emergency and Critical Care and the AVMA, rapid cooling started before you reach the vet is one of the strongest predictors of survival. The goal is to bring the temperature down quickly but safely.

  1. Move the pet to a cool, shaded area immediately. Get out of the sun and into airflow if possible.
  2. Apply cool — not ice-cold — water to the body. Pour it over the pet, soak a towel and drape it over them, or place them in a shallow tub of cool water. Research suggests that tepid to cool water is more effective than ice water, because extreme cold causes blood vessels to constrict and actually slows cooling.
  3. Focus on the belly, armpits, groin, and paw pads, where blood vessels run close to the surface and heat exchange is most efficient.
  4. Use a fan on the wet pet to boost evaporative cooling.
  5. Offer small amounts of cool water to drink if the pet is alert, but never force water into an unconscious animal.
  6. Call your veterinarian or the nearest emergency clinic immediately and transport the pet as soon as possible, continuing to cool them in the car with a wet towel and air conditioning on high.

Stop active cooling once the pet's temperature reaches around 103°F (39.4°C), because continued cooling can tip them into hypothermia. Even if your pet seems to recover, they must still see a veterinarian. Heatstroke can cause delayed organ damage — to the kidneys, liver, gastrointestinal tract, and clotting system — that only becomes apparent hours later. Pets that appear fine after a cooling episode have died days later from these complications, which is why professional evaluation is non-negotiable.

The Bottom Line

Heatstroke is common, fast, and often fatal — but it is also almost entirely preventable. Know your pet's risk factors, plan around the heat rather than through it, and have a clear emergency plan for hot days. If you ever find yourself debating whether conditions are safe for a walk or a car ride, treat the uncertainty itself as a signal to play it safe. The small inconvenience of a delayed walk is nothing compared to the alternative.