Heat Stroke: What Happens In The Dog's Body?

by Jennifer Coates, DVM

Every summer, veterinarians warn about the dangers of excessive heat for dogs.  

Heat stroke, which is characterized by a body temperature between 106 and 109°F (normal is 101.5°F give or take a degree), is most likely to develop when one or more of the following conditions is met:
  • hot and humid weather combined with exercise and/or a lack of shade and access to water
  • being confined in a car or other location where heat can build up
  • obesity
  • advanced age
  • heart disease
  • upper respiratory disease (e.g., laryngeal paralysis or brachycephalic airway syndrome)

But what exactly happens when a dog’s body temperature reaches 106°F or above, and why is it so dangerous?

Photo Lindsey Kone

First, as a dog’s temperature begins to climb, the body cools itself via panting, drooling, and dilating blood vessels on the surface of the body (vasodilation).

These mechanisms are sufficient up to a point, but if there is no relief from high external temperatures, the dog’s excessive panting, drooling and vasodilation leads to dehydration and low blood pressure. 

These conditions inhibit the body’s ability to cool itself, setting up a vicious cycle wherein the hotter the body becomes, the less effective are its mechanisms to deal with the situation.

When body temperatures reach the danger zone, proteins break down, cell membranes are damaged, and the body can no longer produce energy at the cellular level.   

As tissues degrade and blood clotting abnormalities develop, the kidneys and liver begin to fail, the lining of the gastrointestinal tract dies, and heart and brain damage occur.

If a body temperature of 110°F is reached, a dog can die within just a few minutes.

Early symptoms of heat stroke include extreme panting, a rapid heartbeat, red mucous membranes, vomiting, and diarrhea.

As his condition worsens, a dog may suffer from difficulty breathing, abnormal bruising, bloody vomit and diarrhea, blue or pale mucous membranes, collapse, seizures, and paradoxically, a lower than normal body temperature.

If you suspect that a dog is suffering from heat stroke, thoroughly soak him with cool water (do not use ice though) and transport him to the nearest veterinary clinic in a car with the air conditioning on or with all the windows open.

Heat stroke has a mortality rate of around 50%, but with prompt and intensive treatment, many dogs can survive!


Jennifer Coates, DVM graduated with honors from the Virginia-Maryland Regional College of Veterinary Medicine in 1999.  In the years since, she has practiced veterinary medicine in Virginia, Wyoming, and Colorado.  She is the author of several books about veterinary medicine and animal care, including the Dictionary of Veterinary Terms: Vet-speak Deciphered for the Non-veterinarian

Jennifer also writes short stories that focus on the strength and importance of the human-animal bond and freelance articles relating to a variety of animal care and veterinary topics.  Dr. Coates lives in Fort Collins, Colorado with her husband, daughter, and pets.

Articles by Dr. Coates:
When Is It An Emergency?
The Other Side Of The Coin: The Cost Of Defensive Medicine 
Common Misdiagnoses (Part 1) 
Common Misdiagnoses (Part 2)
Dog Allergies: Common, Commonly Misdiagnosed, or Both? 
The Perplexities of Pancreatitis 
Don’t Forget the Physical Therapy
Picking the Right Dog to Breed 
To Neuter Or Not To Neuter… That Is The Question 

Related articles:
Signs, Symptoms And Treatment Of Heat Stroke In Dogs
Know Your Dog's Enemies: Heat Stroke Is No Light Matter! 
Hypo- Versus Hyperthermia


  1. My 5-year-old dog died today of heat stroke and we are all just so devastated. She was not outside more than 10 minutes at a time and we have a cool, air-conditioned house. I did notice she was panting but just thought she was hot (it is 100 degrees here in Kansas City). She had plenty of water and drank a lot. The vet thought her hypothalamus could have been damaged but he wasn't sure. I can't help but feel 100% responsible for her death and am just beside myself. I should have recognized that she was hotter than usual. Ignorance is no excuse and I will have to live with this. It is just horrible. I never post comments but just want others to learn from this. Take your dog panting and acting differently seriously. She died within a very short amount of time. She was the best dog in the world and we loved her so much. We rescued her 3 years ago and she was truly the best. We love you, Toffee....

    1. Tears are rolling down my face as I type this.. My beloved Leia suffered the same fate under the same circumstances... I feel 100% responsible for her dead as well, just like you I saw the symptoms and thought it was her normal panting after our regular afternoon jog. She died outside in d backyard while I was having dinner in the kitchen. Went outside to check up on her and she was gone. An absolute painful and horrible experience, the fact that she died because of my incompetence and/or ignorance and wasn't there for her when she needed me the most. :'(

    2. Art, I am so so sorry about Leia :-( Heatstroke happens so easily on hot and humid days. I'm so sorry.

    3. I lost my sweet boy yesterday to heat stroke. I feel so guilty and like a horrible person. I loved him soso much. It was only 80 degrees. It was morning. Now my boy is gone forever and this pain is bigger than I ever imagined. Thanks for sharing.
      In memory of Angus who was thoroughly and completely loved. I'm so sorry buddy. I'm so sorry.

    4. Andrea, so sorry about your baby. Sadly, something like that can happen quite quickly. Not just temperature, but humidity, breed, amount activity ... all these play role. Dogs don't really understand how to pace themselves.

  2. OMG, that is so terrible! :-( I'm so sorry. 100 degrees IS quite hot. Still, though, it would depend on other factors - the amount of exercise she got while out, whether it was in the shade or on the sun ...

    ... I think your vet might be right that the heat was not the only issue. Hypothalamus is the temperature "control center". If not functioning properly, the body wouldn't cool itself properly.

    Though of course mild to moderate exercise in hot conditions causes an increase in core temperature and heat dissipation become inadequate to expel the heat load and eventually can lead to heat stroke.

    It could be that in Toffee's case it was a combination of the two factors.

    There are other signs of dangerous body temperature besides panting, such as gum and tongue color. Dogs can pant from exercise and excitement also. While I watch the level of panting, I keep a close eye on the gum and tongue color also. (you can check the Signs, Symptoms And Treatment Of Heat Stroke In Dogs article for all the signs one can watch for.

    My heart goes out to you, not only for Toffee, but also because you're blaming yourself. This makes the pain 100x worse. (((hugs)))

    If you'd like to write up Toffee's story as a feature article, please let me know. It might save lives of many other dogs.


  3. Thank you, Jana. Your words of support do help. I would be happy to write up Toffee's story. My husband and I have been over it and over it. When we rescued Toffee (3 years ago), she was positive for heartworms. We ran her through the aggressive Heartgard treatment and she tested negative after that course of treatment. We cannot help but wonder if she had an underlying heart issue that may have contributed to this issue. Although, she was active and always had good energy levels.

    She was a Chow/German Shephard mix that had a rough start in life (heatworms, neglect, surgery to remove an embedded pinch collar, mange). We adopted her despite her problems because we just had a good feeling about her. She had a great life with our family until the end. I'm still so sad and will be for a long time.

    I never heard of or knew to check their gums, tounge and other signs and I like to think that I am a fairly intelligent person. For that, I think it is important to get the word out to others to stress the importance of signs and symptoms - and that they don't have to be outside for a long time to suffer death!

    Thank you for your words and let me know if you would like me to write her story and how to go about it.

  4. You know, it could well be, the heartworm itself can cause heart damage and the treatment is also very hard on the system.

    Oh, wow, embedded pinch collar, that's so sad.

    Having a great life with you is what it is all about. You gave her all you could. At the end that's all that matters.

    Understanding what heatstroke can do to a dog's body and what signs to watch for is important. That's why this information can never be repeated enough. Having a real life tragedy as an example might be just what is needed to open people's eyes.

    Yes, I'd love it if you wrote up Toffee's story. There are a number of real life stories on my blog already, you can take a peak how they're done.

    Generally it includes an introduction about the dog and your relationship, and then an account of what happened, including all symptoms noticed (or missed), what had been done to treated and the outcome.

    My email is in the About Me section.

    My heart really goes out to you. But you gave Toffee couple great years full of love she wouldn't have had otherwise. Without you she might have had been long gone.


  5. My dog, a 13 year old Golden Retriever, got heat stroke last night after taking a walk at 5 pm in Raleigh, NC. The whole country is going through a heat wave, and stupidly I thought if I walked the dogs in the shade and on grass they'd be ok. The younger ones were, but obviously you can't avoid the sun everywhere and when we got home he collapsed. His panting was extreme, and he couldnt drink water. We covered him with wet towels and called the vet. The had me take his temp, which was 107.3, so we raced him to the animal hospital where they immediately hooked him up to fluids, sprayed him with cool alcohol and fans, and he stayed overnight while they ran tests. He was released today and will stay inside except to go to the bathroom, and be on a diet of i.d. meatballs and prilosec and pepcid. We are extremely lucky - what saved him was getting him immediate attention.

    1. So sorry about your guy, wow, 107.3 is very high. Glad he made it. Heat is treaturous, one cannot be too careful.

  6. I would want to look into the cause behind the poor temperature regulation.

    What bread is it? Brachycephalic breeds, such as Bulldogs, Boxers ... typically have harder time with temperature regulation and can overheat easier.

    What is the dogs' body condition? Overweight dogs also have a harder time.

    Dogs with hormone issues (thyroid, adrenals) can also have difficulty regulating their temperature.

    I'd want to look into a cause.

  7. Hi Jennifer, My name is Lindsey Kone. I see that you have used one of my photographs of my dog Bongo from my Flickr account. All of my photos are licensed under the Creative Commons License, which means they are free to be used as long as a) they are not manipulated in anyway and b) there is clear acknowledgement of credit to the artist. I won't ask you to remove my work if you credit it back to it's owner under the photograph. Thank you

    1. Hi Lindsey. Thank you for your note. The credit actually was embedded with the photo (if you roll over you can see it and it has a link to your flickr.)

      However, I added the credit underneath as well.

      Great photo!

  8. My family and I recently lost our amazing bulldog. I’m so sad because we were out of town at the time. We had the ac running for them and water inside and outside in their dog run. We had family come and check on them as well feed them since we left Friday evening and knew we would be back Sunday morning...we didn’t think this would happen. We thought both our bulldogs would be ok. Unfortunately our family had let them out through the slider and made sure they had water, played with them, and fed them. He had figured they would come through their doggy door that was located in their dog run area, what he forgot is the gate was shut when he left. All I can think about is him being so close to water, a cool environment, his home..... I keep thinking about the what ifs and if we just did stay home instead of going to the beach. I feel like this is my fault. I just wish I could give him all the love and attention he deserved right now. I am grateful our other bulldog made it but it’s still hard. He was our baby boy and we had picked him the same time we found out we were pregnant. Our daughter adored him and he loved her back. I just miss my baby boy.

    1. So sorry about your baby :-( Sometimes bad things happen in spite of best intentions. And sometimes really weird and unfortunate things might happen for a reason even though we don't know it.

    2. Thank you for your response. The last few days have been rough. I can’t stop thinking about him especially in our home, this was his home, safe place and a stupid gate killed our dog. We never considered the negative of having a dog run. Never would it cross my mind it could kill our dog.

    3. Yes, takes time; the grief is real and much worse when one feels something could have been prevented. Nobody can always think of everything.

  9. Hi Everyone- I too am going through this grief. My 2.5 year old golden (best dog in the world) loved to run on her "bike tow leash" with my bike. I took her out two days ago on a cool night, and we ran for about 2 miles. She collapsed a block from our house. We took her to the vet, and they said she had a heat stroke. After 24 hours in the hospital and two bags of plasma, she declined and we had to put her down. It was and is absolutely awful. If I had only picked up on some possible cues from her, run a shorter distance, not run at all... This feeling of guilt and responsibility is overwhelming. My heart goes out to anyone who has experienced this shock.

    1. Emily, I'm so sorry about what happened to your baby. Unfortunately, what might seem a cool night can still be dangerous if the humidity is high. And a long, intensive run can be too much. I'm so sorry this happened to you.

  10. I'm so sorry for your loss. I know accepting his loss is very hard for you and to your family. But I know you can cope up like me. When 7 years old dog pet died also in a heat stroke. We are grieving to the loss of our pet. After his pet cremation in hampton roads we give our time to grief and we get another pet trying to forget the pain.


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