Heatstroke in dogs: signs, first aid and prevention

A long midday walk in July, a game of fetch that goes on too long, or ten minutes in the car "while I run into the store." That's how many cases of heatstroke in dogs begin. It's an emergency that can turn fatal quickly, and in most cases it's preventable.

Dogs barely sweat. They shed heat mainly by panting and, to a small degree, through their paw pads. When it's hot or humid, or a dog can't stop moving, that system gets overwhelmed and body temperature climbs unchecked. This guide covers the signs by stage, the right first aid, the mistakes that make things worse, which dogs are most at risk and how to prevent it.

What heatstroke is and when it starts

A dog's normal body temperature is about 101 to 102.5 °F (38.3–39.2 °C). It can rise briefly after exercise, but above roughly 106 °F (41 °C), proteins in the body's cells start to break down and organs such as the kidneys, intestines, liver, brain and the blood-clotting system begin to fail. That's heatstroke: overheating the body can no longer correct on its own.

Heatstroke isn't a fever. With a fever, the body deliberately raises its temperature to fight an infection; with heatstroke, heat builds faster than the body can get rid of it. Fever reducers don't help, and human ones like acetaminophen and ibuprofen are toxic to dogs. If you don't have a thermometer, don't wait to measure: the symptoms are enough to act on.

Signs of heatstroke in dogs

Signs progress quickly, sometimes within minutes:

A dog who pants hard after running and settles within a few minutes in the shade is usually fine. What's worrying is panting that won't stop, panting with any other sign in the table, or heavy panting at rest. If you're unsure what's normal, read why your dog is panting so much.

What to do if your dog has heatstroke: first aid

Every minute counts. Studies of dogs treated for heatstroke have found that those cooled by their owners before arriving at the clinic were more likely to survive. The rule is cool first, then transport, without delaying the trip by more than a few minutes.

1. Stop all activity and move your dog to shade or a cool, ventilated spot, ideally with air conditioning.
2. Wet them with cool tap water, not ice water, all over the body, focusing on the neck, armpits, groin and belly. A small or medium dog who is conscious can go into a tub or kiddie pool of cool water, always with the head above water.
3. Get air moving with a fan or open car windows. Evaporating water is what does the cooling.
4. Offer small amounts of water to drink if your dog is alert and willing. Don't force it or pour water into the mouth of a confused dog, since they could inhale it.
5. Check rectal temperature every 5 minutes if you have a thermometer, and stop active cooling at about 103 °F (39.5 °C) so you don't overshoot.
6. Call ahead and head to the vet without delay. On the way, keep the AC on high and your dog wet and in the airflow.

Keep these steps with the rest of your dog first aid plan.

What not to do

• Don't use ice water, ice cubes or ice packs. They constrict blood vessels in the skin, trap heat inside and can trigger shivering. Cool tap water is enough.
• Don't drape wet towels over your dog. As they warm up, they hold heat in like a blanket. Put them underneath instead, or keep re-wetting the coat without covering it.
• Don't give fever medicine. It doesn't work for heatstroke, and human pain relievers are toxic to dogs.
• Don't wait to see if it passes. A dog who stands back up can still have internal damage.

Why your dog needs a vet even if they seem fine

Extreme heat injures tissues you can't see. Over the next 24 to 72 hours, dogs can develop severe clotting problems, kidney failure, intestinal damage with bloody diarrhea, brain swelling with seizures or heart rhythm problems. Catching these early changes the outcome.

At the clinic, your vet will continue controlled cooling, give IV fluids and oxygen if needed, and run blood work and clotting tests to check organ function. Many dogs stay in the hospital for a day or more for monitoring. The outlook depends on how high the temperature got, how long it stayed there and how quickly cooling started.

Which dogs are most at risk of heatstroke

Any dog can overheat, but risk is clearly higher for:

• Flat-faced (brachycephalic) breeds: English bulldogs, French bulldogs, pugs, boxers, shih tzus, Boston terriers, Pekingese, Cavalier King Charles spaniels and Dogues de Bordeaux. Narrow nostrils and an elongated soft palate make panting much less effective.
• Thick-coated and northern breeds: huskies, malamutes, chow chows and Samoyeds.
• Overweight dogs: fat insulates and makes every effort harder. If that's your dog, see our guide to overweight dogs.
• Puppies and seniors, who regulate temperature less efficiently.
• Dogs with heart or airway disease, such as laryngeal paralysis or collapsing trachea.
• Large and giant breeds, and high-drive dogs that won't stop on their own: retrievers, herding and hunting breeds, or any dog who'll chase a ball until they drop.

A large study of UK veterinary records from the Royal Veterinary College's VetCompass program found that exercise was the most common trigger of heat-related illness, far ahead of hot cars. In other words, the walk or play session at the wrong time of day is the most common danger.

Hot cars: dangerous in minutes

A parked car heats up much faster than most people expect. According to figures widely cited by the AVMA, on a 70 °F (21 °C) day the inside of a car can reach 89 °F (32 °C) in 10 minutes and 104 °F (40 °C) in 30 minutes. On a 90 °F (32 °C) day, it can hit 109 °F (43 °C) within 10 minutes. Cracking the windows barely makes a difference.

If you're road-tripping together this summer, plan for shady stops, water and AC; see our tips for traveling by car with a dog.

How to prevent heatstroke in dogs

• Walk early in the morning and late in the evening. During heat waves, keep midday outings to short bathroom breaks.
• Skip intense exercise when it's hot or humid, even if the temperature doesn't seem extreme. Build mandatory shade breaks into fetch sessions.
• Always have cool water available, including on walks, plus shade at home and in the yard.
• Use a basket muzzle if your dog needs one; fabric muzzles that hold the mouth closed prevent panting.
• Don't shave double-coated dogs: the coat helps insulate them from heat. Brush often to remove dead undercoat instead.
• Be extra careful during the first hot days of the year, before your dog has acclimated.

For hot pavement, beach days, pools and the rest of warm-weather care, see our summer dog care tips.

Frequently asked questions

What temperature is too hot for dogs?

There's no single number, because humidity, exercise, breed, weight and acclimation all matter. A flat-faced dog can struggle in mild weather if they're exerting themselves, and any dog is at risk in a parked car even when it's only 70 °F (21 °C) outside. As a rough guide, scale back exercise from about 77 °F (25 °C) when it's humid and avoid it during the hottest hours above 86 °F (30 °C).

How quickly can a dog get heatstroke?

It can happen in a matter of minutes, especially in a car or during hard exercise on a hot, humid day. High-risk dogs such as brachycephalic breeds can go from heavy panting to confusion very fast. That's why it's best to act at the first signs instead of waiting to see whether things get worse.

Can a dog fully recover from heatstroke?

Yes, many dogs recover completely when they're cooled quickly and get prompt veterinary care. The outlook gets worse the higher the temperature climbed, the longer it lasted and the later treatment began, and if seizures, clotting problems or kidney failure develop. The first 24 to 72 hours are the most critical, which is why vets often recommend hospitalization or close monitoring.

Do cooling mats and cooling vests work?

They can help as extras on hot days, especially for high-risk dogs, but they don't replace shade, water and limiting exercise. Evaporative vests work less well in high humidity. Supervise gel cooling mats with dogs who chew, and never treat a vest as permission to walk during the hottest part of the day.

Is it OK to give my dog ice cubes in summer?

As a treat on a hot day, an ice cube or a homemade frozen treat made with dog-safe fruit or low-sodium broth is a fine way for a healthy dog to cool off. What you shouldn't do is use ice to treat heatstroke that's already happening. In that case, wet your dog with cool water, add airflow and call your vet.

Sources

• Royal Veterinary College (VetCompass program): studies of heat-related illness in dogs seen at UK veterinary practices.
• Merck Veterinary Manual: heatstroke and hyperthermia in small animals.
• American Veterinary Medical Association (AVMA): pets in hot vehicles.
• ASPCA: hot weather safety tips for pets.