Heatstroke in Dogs: Signs, First Aid and Prevention

What it is

Heatstroke happens when a dog's body temperature climbs faster than the dog can shed heat. Dogs can't cool off by sweating the way people do, so they rely mainly on panting, and panting works poorly in heat, high humidity, or a restricted airway. A normal temperature is roughly 100.5 to 102.5°F (38 to 39.2°C). Veterinary sources draw the heatstroke line a little differently: PetMD uses 104°F (40°C), Cornell 105°F (40.6°C), and AKC 105.8°F (41°C). Treat any reading of 104°F or higher in an overheated dog as an emergency.

Left uncooled, the heat damages tissue throughout the body. The kidneys, gut, brain, heart, and blood-clotting system can all be affected, which is why vets treat heatstroke as an emergency even when a dog seems to bounce back. AKC describes three stages: heat stress (mild panting, thirst), heat exhaustion (heavy panting, drooling, tiredness), and heatstroke (collapse or other severe signs).

Outcome depends on how high the temperature got, how long it stayed there, and how fast cooling and treatment began. Dogs that have had heatstroke can be more prone to it again. If your dog is panting hard but the weather is mild, see panting in dogs for other possible causes.

Causes and risk factors

What you can do at home

Heatstroke is not something to manage at home, but what you do in the first few minutes matters. Call your vet or the nearest emergency clinic as you start cooling so the team can prepare for your arrival.

Move your dog into shade or an air-conditioned space. Wet your dog with cool or room-temperature water, focusing on the belly, armpits, and paws, and aim a fan at your dog if you have one. In the car, point the air conditioning toward your dog. If your dog is alert and able to drink, offer small amounts of room-temperature water.

Do not use ice, ice packs, or ice-cold water, which can push a dog toward shock and overcooling, and do not use rubbing alcohol. Cooling is not a cure on its own: a dog that looks better still needs a veterinary exam, because internal damage may not be visible.

If you own a rectal thermometer and can use it without slowing you down, a reading helps your vet, but do not delay leaving to take one. Dogs can be cooled too far, so let the vet take over the cooling once you arrive.

What happens at the vet

The vet will ask what happened: how long your dog was in the heat, whether there was exercise, shade, or water, and whether your dog has heart or airway problems or takes regular medications. Tell them what cooling you have already done, since that affects the temperature reading.

Your dog's temperature, gum color, hydration, mental state, heart, and breathing are checked right away. Blood tests and a urine test look for damage to the kidneys, liver, and clotting system, and an electrocardiogram may be added to check heart rhythm.

Treatment is supportive and happens in the hospital. Controlled cooling continues with the temperature monitored closely, and VCA notes it is stopped at around 103°F (39.4°C), before the temperature reaches normal, because overcooling causes its own trouble. Intravenous fluids, oxygen, and medicines for vomiting, diarrhea, or seizures are common. Some dogs also need plasma or other blood products.

Most dogs that survive the first day or so recover over a few days of hospital care, although some are left with lasting organ damage. A recheck with blood work a week or two later is common. Your vet can tell you what recovery is likely to look like for your dog.

Prevention

Prevention comes down to never putting your dog in a position where heat can win. Never leave your dog in a parked car, not even for a quick errand and not with the windows cracked. The AVMA notes that a car's interior can climb about 20°F (11°C) in just 10 minutes, even on a day that doesn't feel hot or in the shade.

On warm or humid days, exercise early in the morning or late in the evening, schedule breaks, and bring water. Always give outdoor dogs shade and fresh water, and keep dogs that are flat-faced, older, overweight, or living with heart or airway disease indoors in air conditioning on hot days. Heat and humidity are a dangerous pair: a day that feels only warm to you can still be too much for a dog that cannot pant efficiently.

Keep your dog at a healthy weight, because obesity raises heatstroke risk (see obesity in dogs). Ask your vet whether any medication your dog takes makes overheating more likely, and avoid muzzles that restrict panting in hot weather. For help matching activity to your dog, our guide on how much exercise a dog needs is a good starting point.