Heat stroke in dogs: signs, first aid and when it is an emergency
Quick answer
Heat stroke is an emergency. If your dog collapses, vomits, stumbles, seems confused or has a seizure in the heat, start cooling with cool water and a breeze, and go to a vet now. (Merck, PDSA)
Heavy panting, drooling and tiredness are the early signs: stop, move to shade, cool your dog and call your vet. Most cases start during exercise, not in hot cars. (Hall et al. 2021, Hall et al. 2020)
Cool and monitor, call your vet
Early signs only: heavy panting, drooling, fast breathing, tiredness.
Emergency: go now
Any collapse, seizure, confusion, vomiting, wobbliness, abnormal gums or blood.
60-second heat stroke symptom checker
Tick every sign you can see now. If in doubt, treat it as an emergency.
What to do
Tick any sign you can see.
In short
Key takeaways
- Cool first, transport second: start cooling where you are, then keep cooling on the way to the vet. (RSPCA, Hall et al. 2023)
- Use cool water and moving air. No ice baths, and no wet towels draped over the dog. (Merck, VCA)
- Exercise caused 74.2% of heat illness in UK dogs; hot cars caused 5.2%. (Hall et al. 2020)
- Flat-faced dogs had 2.10 times the odds, and dogs over 50 kg 3.42 times. (Hall et al. 2020)
- Even after treatment, watch your dog closely for 24 to 48 hours. (PDSA)
Recognise it
Signs of heat stroke in dogs, from mild to severe
Heat stroke happens when a dog cannot shed heat fast enough, in hot and especially humid weather or during hard exercise. A 2021 study proposed grading it by signs, and found the signs predict the outcome better than the thermometer does. (Bruchim et al. 2017, Hall et al. 2021)
| Stage | What you see | What to do |
|---|---|---|
| Early (mild) | Heavy panting, drooling, fast breathing, tiredness, slowing down (Hall et al. 2021, PDSA) | Stop, shade, cool, call your vet |
| Moderate | Vomiting or diarrhoea, collapse that comes and goes, a single seizure, bright red gums (Hall et al. 2021, PDSA) | Emergency: cool and go now |
| Severe | Confusion, stumbling, repeated seizures, unresponsiveness, blood in vomit or diarrhoea (Hall et al. 2021, PDSA, RSPCA) | Emergency: cool and go now |
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Act now
Heat stroke first aid for dogs, step by step
These steps follow Merck and the AVMA, with the cooling detail the RSPCA, PDSA and VCA add. Start straight away: in one hospital study, arriving more than 90 minutes after the dog fell ill was a risk factor for death. (Merck, AVMA, Bruchim et al. 2006)
- Stop and move your dog out of the heat. Stop all exercise and move your dog into shade or a cool room, out of direct sun. Keep it calm, and do not try to stop it panting: panting is how it cools. (Merck, AVMA, VCA)
- Cool with cool water, not ice. Pour or hose cool water over the body, especially the belly and between the hind legs, and sweep it away with your hands as it warms. Do not plunge your dog into ice-cold water, use an ice bath or put ice on the skin. (AVMA, Merck, Merck, VCA)
- Add moving air. Use a fan, air conditioning or an open window. Water plus moving air is the cooling method the research recommends. (Merck, VCA, Hall et al. 2023)
- Offer small sips once cooling starts. Offer small amounts of water once your dog begins to cool. Encourage it, but never force a dog to drink. (Merck, VCA)
- Call ahead and go to the vet, cooling on the way. Phone the nearest vet to say you are coming, then go as soon as possible. Keep cooling in the car with air conditioning or open windows, and take a second person if you can. (AVMA, Merck, RSPCA, PDSA)
In the clinic, vets stop active cooling once the temperature falls to about 103°F (39.4°C), to avoid overshooting into hypothermia. At home without a thermometer, keep cooling until you reach the vet and let them take over. (VCA, VCA)
Fact check
Cold water, ice and wet towels: where the sources disagree
The veterinary sources do not all say the same thing, and old advice spreads easily. In UK practice records, wet towels were the most common cooling method and only 21.70% of dogs were cooled before the journey to the vet, so the details matter. (Hall et al. 2023)
| Question | What the sources say | What we advise |
|---|---|---|
| Cool or cold water? | Merck and VCA: cool, not cold, and never submerge in cold water. RSPCA and PDSA: cold tap water is fine and rarely causes shock (Merck, VCA, RSPCA, PDSA) | Plenty of cool or tap water poured over the body. No plunging |
| Ice? | Merck mentions ice packs; VCA says they are no longer recommended; the VCA handbook says no ice water, ice baths or ice (Merck, VCA, VCA) | No ice baths and no ice on the skin |
| Wet towels? | Merck and the AVMA use wet towels on the belly or around the neck; VCA, RSPCA and PDSA say never drape them over the body, as they trap heat (Merck, AVMA, VCA, RSPCA) | Do not cover the dog. A cold wet towel underneath it is fine |
| Cool first or drive first? | The AVMA brochure goes to the vet first and cools if that is not possible at once; the RSPCA and a 2023 study say cool first, transport second (AVMA, RSPCA, Hall et al. 2023) | Start cooling at once, then go, cooling on the way |
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Numbers
What body temperature is heat stroke in dogs?
A dog’s normal rectal temperature is about 101.5 to 102°F (38.6 to 38.9°C). The lines above it differ by source: (Merck)
- Above 103°F (39.4°C): abnormal, or hyperthermic. (VCA)
- Above 104°F (40°C): at risk of heatstroke, PDSA’s more cautious line. (PDSA)
- 106°F (41.1°C) or higher: heat stroke, a dangerously high temperature that is not a true fever. (Merck, VCA)
- Around 107 to 109°F (41.2 to 42.7°C): multiple organ failure. (VCA)
Do not wait to take a temperature before acting. The 2021 grading study found that the signs a dog shows predict the outcome better than its temperature, and that spotting the milder signs early gives owners time to act. (Hall et al. 2021)
Who is at risk
Heat stroke risk factors in dogs
A UK study of dogs in first-opinion practices found that heat-related illness killed 14.18% of the dogs it affected, and identified who is most at risk. (Hall et al. 2020)
| Risk factor | What the research found |
|---|---|
| Flat-faced (brachycephalic) skull | 2.10 times the odds of mesocephalic dogs (Hall et al. 2020) |
| Breed | Compared with Labradors: Chow Chow 16.61, Bulldog 13.95, French Bulldog 6.49, Greyhound 4.26, Cavalier 3.45, Pug 3.24 times the odds (Hall et al. 2020) |
| Body weight | Over 50 kg: 3.42 times the odds of dogs under 10 kg; at or above the breed’s average weight also raised the odds (Hall et al. 2020) |
| Age | Dogs aged 12 or more had 1.75 times the odds of dogs under 2 (Hall et al. 2020) |
| Obesity | A risk factor for death in a hospital series (Bruchim et al. 2006) |
| Thick coat, medical conditions, muzzles | Named as raising the risk; a muzzle restricts panting (VCA, VCA) |
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What sets it off matters as much as who it happens to. In UK records, exercise triggered 74.2% of events, hot weather alone 12.9% and vehicles 5.2%. The study concluded that exercise in the heat affects and kills more dogs than hot cars. (Hall et al. 2020)
Cars
Dogs in hot cars: how fast a car heats up
Merck gives the example of an 85°F day: inside a car it can pass 100°F in 10 minutes and 120°F in 35 minutes, even with a window open or parked in shade. The RSPCA says that at 22°C outside, a car can reach 47°C within an hour. (Merck, RSPCA)
Never leave a dog in a parked car on a warm day, not even for a quick errand. If you see a dog in distress in a hot car, call the emergency services. (Merck, RSPCA)
Prevent it
How to prevent heat stroke in dogs
- Check the weather before exercise. Our walk temperature checker gives a verdict for your dog, and the India version works in °C. Dog deaths rose once daily highs passed 25°C (77°F). (Tripovich et al. 2025)
- Walk early or late, keep games short, and stop at the first sign of heavy panting. (Hall et al. 2021, RSPCA)
- Give shade and fresh water at all times, and never leave a dog in a car. (Merck, RSPCA)
- Keep your dog at a healthy weight: obesity is a risk factor, and the weight loss planner shows how long a safe plan takes. (Bruchim et al. 2006, Hall et al. 2020)
- Take extra care with flat-faced breeds, which can overheat from excitement even on cool days. (Merck)
Water
Dog dehydration signs and how much water a dog needs
Dehydration and heat illness go together. The RSPCA describes dehydration as a dry nose, sunken eyes, heavy panting, less urine and tiredness, and PDSA says dry, sticky gums can be a sign. Water should never be restricted for a healthy dog. (RSPCA, PDSA, Merck)
Water intake calculator
Daily water, as a guide
Enter the weight to see the range.
Rough dehydration checks
- Skin tent: gently lift the skin on the back of the neck. It should snap back within one second; if it stays tented, your dog may be dehydrated. (VCA)
- Gums: they should feel moist. Press a finger on the gum; the white patch should turn pink again in under two seconds. Dry, sticky gums can mean dehydration. (PDSA) (Merck)
- These are rough checks. Merck says estimating dehydration is always somewhat subjective, and skin tests mislead in old, very thin and very young dogs. If you are worried, call your vet. (Merck)
The calculator uses Merck’s maintenance range of about 44 to 66 ml per kg a day. Merck gives it for most mammals rather than dogs alone, and it applies in mild conditions; VCA says active dogs and dogs in warm weather need more, without a figure. (Merck, VCA)
Drinking far more than usual can be a sign of illness. VCA says normal intake is significantly less than 100 ml per kg a day, so a dog drinking that much on an ordinary day should see a vet. (VCA)
Afterwards
Heat stroke recovery and after-effects
Most healthy dogs recover quickly if their temperature did not climb too high, and the quicker a dog is cooled, the better its chance of a full recovery. (VCA, PDSA)
Severe heat stroke can cause clotting problems and damage the kidneys, brain, gut, heart and lungs. In one hospital study of 54 dogs, half died; a clotting disorder affected 28 and acute kidney failure 18, and both were risk factors for death. (PDSA, Bruchim et al. 2006)
That is why a dog that seems fine should still see a vet. PDSA advises watching closely for 24 to 48 hours after treatment, VCA notes that some dogs die later from complications, and a dog that has had heat stroke is at greater risk of another. (PDSA, VCA)
Afterwards, build exercise back up slowly and plan walks around the weather. The daily exercise calculator shows your dog’s usual needs, and why does my dog pant so much covers which panting is normal. If anything about your dog worries you, our behaviour checker helps decide how urgent it is.
Your vet
When to see a vet
FAQ
Questions people ask
- What are the first signs of heat stroke in a dog?
- Heavy panting that does not settle, more drooling than usual, fast or noisy breathing, and a dog that slows down, seems tired or lies down on a walk. PDSA also lists bright red gums. Treat these as the warning: stop, move to shade, cool your dog and call your vet. Vomiting, wobbliness, confusion or collapse mean go to a vet now. (PDSA, Hall et al. 2021, PDSA)
- What do I do if my dog has heat stroke?
- Move your dog out of the heat, pour cool water over its body, especially the belly and between the hind legs, and add moving air with a fan or open window. Offer small sips once it starts to cool. Call the nearest vet and go straight there, cooling on the way. The UK charities sum it up: cool first, transport second. (Merck, AVMA, RSPCA)
- Should I use cold water or ice to cool my dog?
- Use cool water and plenty of it. Merck and VCA say cool, not cold, and never submerge a dog in cold water. The RSPCA and PDSA say cold tap water is fine and rarely causes shock. All agree that ice baths and ice on the skin are out. Do not drape wet towels over the dog: they can trap heat. (Merck, VCA, RSPCA, PDSA)
- What body temperature is heat stroke in dogs?
- Normal is about 101.5 to 102°F (38.6 to 38.9°C). VCA calls anything above 103°F (39.4°C) hyperthermic, PDSA says a dog above 104°F (40°C) is at risk, and Merck and VCA put heat stroke at 106°F (41.1°C) or higher. A 2021 study found the signs predict outcome better than the thermometer, so act on the signs. (Merck, VCA, PDSA, Hall et al. 2021)
- How long does it take a dog to recover from heat stroke?
- Most healthy dogs recover quickly if their temperature did not get too high, but some suffer organ damage or die later from complications. PDSA advises watching a dog closely for 24 to 48 hours after treatment. Severe heat stroke can cause clotting problems and kidney damage, and a dog that has had it is at greater risk of another episode. (VCA, PDSA)
- Can a dog get heat stroke on a mild day?
- Yes. Exercise caused 74.2% of heat-related illness in UK dogs, against 5.2% from hot cars, and cases happen in ordinary British summers. Merck notes that short-nosed breeds can overheat from excitement even on cool days. Check the weather and your dog with our walk temperature checker before an energetic walk or game. (Hall et al. 2020, Merck)
Sources
Where this comes from
Every figure and threshold on this page comes from the veterinary sources below, and each one is linked where it is used. Where no source gives a cut-off, we say call your vet rather than invent one.
What to do in a dog or cat emergency
Merck Veterinary Manual - dated December 2025 - read 2026-10-28
merckvetmanual.comProtecting pets during hot summer months
Merck Veterinary Manual - dated May 28, 2025 - read 2026-10-28
merckvetmanual.comFever of unknown origin in dogs
Merck Veterinary Manual - dated September 2024 - read 2026-10-28
merckvetmanual.comPet first aid (client brochure)
American Veterinary Medical Association - read 2026-10-28
ebusiness.avma.orgHeat stroke in dogs
VCA Animal Hospitals - dated July 10, 2025 - read 2026-10-28
vcahospitals.comPet emergency care handbook: what to do when emergencies happen
VCA Northwest Veterinary Specialists - read 2026-10-28
vcahospitals.comSenior dog care: special considerations
VCA Animal Hospitals - dated July 17, 2026 - read 2026-10-28
vcahospitals.comNutrition for working and service dogs
VCA Animal Hospitals - dated April 14, 2026 - read 2026-10-28
vcahospitals.comNutritional requirements of small animals
Merck Veterinary Manual - dated September 2024 - read 2026-10-28
merckvetmanual.comThe fluid resuscitation plan in animals
Merck Veterinary Manual - dated November 2025 - read 2026-10-28
merckvetmanual.comParameters to evaluate during triage
Merck Veterinary Manual - read 2026-10-28
merckvetmanual.comHeatstroke in dogs (Pet Health Hub)
PDSA - dated September 2023 - read 2026-10-28
pdsa.org.ukFirst aid for heatstroke
PDSA - dated September 2023 - read 2026-10-28
pdsa.org.ukAre my dog’s gums pale?
PDSA - dated October 2022 - read 2026-10-28
pdsa.org.ukHow to recognise and treat heatstroke in dogs
RSPCA - read 2026-10-28
rspca.org.ukHeatwave pet care myths: we debunk ten common misconceptions
RSPCA - dated 4 July 2025 - read 2026-10-28
rspca.org.ukDogs die in hot cars
RSPCA - read 2026-10-28
rspca.org.ukSummer fun in the sun: hot weather safety tips for your pets
ASPCA - dated August 16, 2018 - read 2026-10-28
aspca.orgIncidence and risk factors for heat-related illness (heatstroke) in UK dogs under primary veterinary care in 2016. Scientific Reports 10:9128
Peer-reviewed (Scientific Reports) - dated 2020 - read 2026-10-28
pmc.ncbi.nlm.nih.govDogs don’t die just in hot cars: exertional heat-related illness (heatstroke) is a greater threat to UK dogs. Animals 10(8):1324
Peer-reviewed (Animals, MDPI) - dated 2020 - read 2026-10-28
pubmed.ncbi.nlm.nih.govProposing the VetCompass clinical grading tool for heat-related illness in dogs. Scientific Reports 11:6828
Peer-reviewed (Scientific Reports) - dated 2021 - read 2026-10-28
pmc.ncbi.nlm.nih.govCooling methods used to manage heat-related illness in dogs presented to primary care veterinary practices during 2016–2018 in the UK. Veterinary Sciences 10(7):465
Peer-reviewed (Veterinary Sciences, MDPI) - dated 2023 - read 2026-10-28
pmc.ncbi.nlm.nih.govHeat stroke in dogs: a retrospective study of 54 cases (1999–2004) and analysis of risk factors for death. Journal of Veterinary Internal Medicine 20(1):38–46
Peer-reviewed (Journal of Veterinary Internal Medicine) - dated 2006 - read 2026-10-28
academic.oup.comFeeling the heat: associations among daily ambient temperatures, extreme heat days and risk mortality in Australian dogs from New South Wales (1997–2017). Australian Veterinary Journal 103(11):717–723
Peer-reviewed (Australian Veterinary Journal) - dated 2025 - read 2026-10-28
pmc.ncbi.nlm.nih.govPathophysiology of heatstroke in dogs: revisited. Temperature (Austin)
Peer-reviewed (Temperature) - dated 2017 - read 2026-10-28
pubmed.ncbi.nlm.nih.gov
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Last reviewed . Estimate only. For health questions, ask your vet.