A dog with heat stroke will pant heavily and excessively, drool, become weak or confused, and may vomit or collapse. A normal dog’s body temperature sits between 100.5 and 102.5°F. Heat stroke begins when that temperature climbs to 105°F or higher and the dog can no longer cool itself down. Recognizing the signs early and acting fast can be the difference between recovery and a life-threatening emergency.
Early Warning Signs
The first signs of overheating are easy to miss because they look like a dog that’s simply hot and tired. Excessive panting, a faster-than-normal heart rate, heavy drooling, and general weakness are the earliest red flags. At this stage your dog’s body is still trying to regulate its temperature, but it’s losing the battle.
As the overheating progresses, you’ll notice the gums become dry or tacky instead of moist. Your dog may start to feel nauseated, vomit, or refuse to move. Some dogs will seek shade or cool surfaces obsessively, lie down and refuse to get up, or stumble when they try to walk. This middle stage is sometimes called heat exhaustion, and it can tip into full heat stroke within minutes if the dog isn’t cooled down.
Signs of a Full Heat Stroke Emergency
Heat stroke crosses into dangerous territory when the brain starts to be affected. At this point your dog may appear confused or disoriented, stagger as if drunk, or briefly faint. Seizures, bloody diarrhea, and complete collapse are all signs of severe heat stroke. Some dogs become unresponsive or slip into a semiconscious state. If you see any of these neurological signs, your dog needs veterinary care immediately.
You don’t need a thermometer to act. If your dog is panting so hard it can barely close its mouth, is drooling heavily, looks dazed, and won’t respond normally, treat it as heat stroke. If you do have a rectal thermometer, a reading of 105°F or above confirms it.
How to Cool Your Dog Safely
Move your dog to a shaded or air-conditioned area right away. Apply cool (not cold) water to the neck, armpits, and groin, where blood vessels sit close to the skin. You can use wet towels, but swap them out frequently because they trap heat once they warm up. Offer small amounts of cool water to drink if your dog is conscious and able to swallow.
There are two common mistakes that can make things worse. First, do not use ice water or submerge your dog in an ice bath. Extreme cold causes the blood vessels near the skin to constrict, which actually traps heat inside the body and can damage organs further. Second, dogs with heat stroke can lose consciousness, so putting an unconscious dog in water creates a drowning risk. Stick with cool water applied gradually, and get to a veterinarian as quickly as possible.
Dogs at Higher Risk
Flat-faced (brachycephalic) breeds like Bulldogs, Pugs, French Bulldogs, and Boston Terriers are significantly more likely to develop heat stroke than dogs with longer snouts. Their shortened airways make it harder to cool air as they breathe, which is a dog’s primary way of regulating temperature. Research has found that skull shape is actually a more significant risk factor than breed classification alone, meaning any dog with a shorter-than-average muzzle faces elevated risk.
Body weight matters just as much, and in some studies even more than breed. Overweight dogs have a harder time dissipating heat regardless of their skull shape. Older dogs and very young puppies are also more vulnerable, as are dogs with thick double coats. Even fit, healthy dogs can develop heat stroke if they exercise too hard in hot weather. In fact, roughly three out of four heat stroke cases in dogs are exertional, meaning the dog overheated from physical activity rather than simply being left in a hot environment.
What Happens at the Vet
Heat stroke can damage multiple organ systems even after the dog’s temperature comes back down. The kidneys, liver, gut lining, and blood clotting system are all vulnerable. In one study of dogs hospitalized for severe heat stroke, nearly half developed kidney injury and more than half developed dangerous clotting problems. These complications can emerge hours or even a day or two after the initial episode, which is why veterinary monitoring matters even if your dog seems to be improving.
Hospitalization for heat stroke survivors typically lasts about 3 days, though it can range from a single day to nearly two weeks depending on severity. The mortality rate for severe cases is high, reported at around 40 to 50 percent even with aggressive treatment. Dogs that receive cooling before arriving at the clinic and those treated earlier in the progression tend to have better outcomes. Speed is the single biggest factor you can control.
Situations That Trigger Heat Stroke
The most obvious scenario is a dog left in a parked car. Even on a 75°F day, the interior of a car can climb past 100°F within minutes. But most heat stroke cases actually happen during exercise: a long run, an intense game of fetch, or a hike on a warm afternoon. Dogs don’t sweat the way humans do. They rely almost entirely on panting to cool down, and when the air is hot and humid, panting becomes much less effective.
Pay extra attention on days above 80°F, especially when humidity is high. Walk your dog early in the morning or after sunset. Keep water available at all times. And watch your dog’s behavior closely. If panting becomes loud, rapid, and uncontrolled, if your dog slows down or lies flat and won’t move, or if the gums look bright red or pale and dry, stop all activity, start cooling, and head to the vet.