Heat Stroke In Dogs: What is it and when does it happen?



Updated: March 29, 2021

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signs of heat stroke in dogsWhat Is Heat Stroke In Dogs?

When a dog’s body temperature rises over 104°F and his mechanisms for cooling himself – such as panting – become overwhelmed and stop working properly, heat stroke sets in.

Sadly it’s not just a dog’s thermoregulatory (“cooling”) system that fails in heat stroke. As the condition progresses and the body temperature rockets even further above 104°F, most body systems fail. Among them are the all-important neurologic, urinary, circulatory, and blood clotting systems. Once these systems begin to fail, the likelihood of recovery from heat stroke is very slim.

While heat stroke can happen quickly, there is often a progression from mild heat stress to the more moderate heat exhaustion before reaching the most severe condition of heat stroke. Since prevention of heat stroke is crucially important, everybody should know and keep an eye out for the “early warning signs.” If you know these warning signs of heat stress and heat exhaustion, you’ll be able to take appropriate steps before the situation progresses to a potentially deadly case of heat stroke.


This is a dog in the early stages of heat stress on an 86° day in a car parked in a covered parking garage. The windows were cracked. Note the non-stop panting.

Help Your Dog Avoid the Heat

  • Heat stroke is a dangerous condition that can threaten your dog’s life.

  • Knowing and responding to the early warning signs that indicate the less severe heat stress and heat exhaustion could save your pet’s life.

  • Heat stroke can happen even on relatively mild days.

  • On hot days, consider adjusting pet’s routine to keep them safe.

Signs of Heat Stress and Heat Exhaustion

Note that there are varying degrees with these signs, how obvious or severe they are, or even how many are noticeable at once — depending on the situation and how long the dog has been in the heat.
  • Moving more slowly than normal, not keeping up
  • Seeking shade and frequent rests
  • Seeking out puddles or other water sources for drinks
  • Persistent or prolonged panting
  • Loud or labored breathing
  • Rapid pulse
  • Dark red gums and tongue
  • Wide, stressed eyes
  • General increased anxiety
  • If in a parked car, these additional signs may be seen:
    • Barking
    • Pacing
    • Seeking out shady spots under the dash or seats
    • Clawing at the window, dash, or seats attempting to escape
    • Attempting to stick their nose or head out a cracked window
    • Slobbery nose or paw prints on the inside of the windows

Signs of Heat Stroke

Again, there are varying degrees and severities of these signs and not all will be present in every case. Also note that the signs listed below are in addition to the signs listed above for heat stress and heat exhaustion, and there is considerable overlap.

  • Vomiting - possibly containing blood
  • Diarrhea - possibly containing blood
  • Drooling
  • Fast, thready pulse
  • Glazed-over eyes
  • Staggering
  • Collapse
  • Unresponsiveness or apparent signs of an altered mental state
  • Seizures
  • Bruising of the skin or the gums (these small, pinpoint bruises, called “petechiae," are often most visible inside the ears or on the underside of the belly)

Learn How to treat heat stroke and heat exhaustion in dogs.

When Does Heat Stroke Happen?

When most people think of or hear about heat stroke in pets, they typically think about dogs left in hot cars. This is a good thing, as it’s certainly a very common cause of heat stroke (and one of the more easily prevented, too!). However, it’s important to recognize that hot cars aren’t the only place where pets suffer from heat stroke.

In cars and other vehicles
Multiple studies have shown how rapidly the temperature can rise in a parked car, even with the windows “cracked” and even on relatively mild days. These are numbers that everybody should be aware of and keep in mind when taking their pets (and kids) in the car.

  • In one study the average rate of temperature rise over the 16-day study period was shown to reach a 19°F increase in just 10 minutes, 29°F in 20 minutes, 34°F rise in 30 minutes, and 43°F in 60 minutes. Anybody who has sat in a parked car on a warm day will appreciate just how uncomfortable any of those increases can be, and just how short a time 10 minutes actually is.

  • In the same study, on one of the (very mild) 72°F days, the temperature inside the car reached a dangerous 93°F in just 10 minutes! And it climbed from there to devastating and deadly levels quickly – reaching 105°F in 20 min., 110°F in 30 min., and 119°F in 1 hour!

  • Another study (also referenced below) showed that 80% of the temperature rise occurs within the first 30 minutes.

  • Two studies that specifically looked at the effect of leaving the windows cracked on the rate of heat rise in parked cars found that cracking the windows does very little — if anything at all — to help prevent heat rise and overall risk for heat stroke.

    • One study showed an insignificant decrease in the rate of heat rise from 6.25°F per 5 minutes (closed windows) versus 5.5°F per 5 minutes (windows cracked) over the first 20 minutes of the study. However, by the end of the 60-minute study period, the two cars reached the same internal temperature.

    • The other study found only a 2°F difference in final internal temperature between windows closed and windows cracked at the end of a 90-minute study period. And this was in spite of the fact that the vehicle with the windows cracked was (1) larger and (2) lighter in color… either of which could easily account for that minimal decrease in heat rise.

As you can see, when it’s hot outside, heat stress can progress rapidly to a debilitating and potentially fatal case of heat stroke for a dog left in a parked car for as few as 10 minutes. Even on a relatively mild 65–75°F day, 15–20 minutes of enclosure in a parked car can be enough to bring on a case of heat stroke in a dog. And this is true regardless of whether the windows are cracked.

Find out what you can do if you see a dog or cat in a hot car and whether it's legal to break the window to rescue the dog.

During outdoor exercise, play, and even walks
Just like us, dogs generate heat when they play and exercise. Unlike us, however, dogs aren’t covered with sweat glands to help them cool off efficiently and effectively. They mainly depend on panting to get rid of excessive heat. Combine that fact with many dogs' love of play and exercise (their “play drive”) and you’ve got a recipe for potential disaster on warm, hot, and/or humid days.

For dogs with certain medical conditions — including brachycephalic syndrome, collapsing trachea, laryngeal paralysis, and even arthritis — even a short walk around the block during the warmer parts of the day can spell disaster.

Your dog counts on you to use caution and good judgment when taking him out for exercise and play on hot days. Always avoid the hotter times of the day and read "Heat Stroke: Is My Dog At Risk?" to see what breed, health, and other factors increase your dog’s risk of suffering from heat stroke.

During travel
Travel — be it by car, RV, plane, or another form — can put your dog at risk for suffering from heat stroke. The dangers are present both during the journey and even once you arrive at your destination. Be aware of these risks, book and plan your travel itinerary carefully, and recognize that your dog may need time to acclimate to the temperatures and humidity levels at your final destination.

When confined outside
Dogs who live outside and those who spend large amounts of time outside during warmer days are at avoidable risk of suffering from heat stroke, too. Reliable shade, plentiful water, and protection from hot asphalt and other surfaces are important to protect outdoor dogs. On hot days, please consider bringing your dog inside for his comfort. Depending on where you live, that might even be the law.


Heat stroke is a devastating emergency and a horrible thing for a pet (and the people who love them) to suffer. Fortunately heat stroke is easily preventable. Please read and share these additional articles to learn your dog’s (or cat’s) risk for heat stroke and learn how to keep your pets safe from heat stroke.