Heatstroke: It Isn't Just Hot Cars
Most UK heatstroke cases followed exercise, often an ordinary walk. Who is at risk, the signs, and the 2026 first-aid advice: cool first, then go.
Written by thecanineledger
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If you think your dog has heatstroke right now: stop all activity and get your dog out of the heat. Run cool water over the body and belly, not the face. Keep it running for about 15 minutes if you can’t take a temperature. Then go straight to the nearest open vet, phoning on the way. That is the 2026 first-aid guidance, set out in §4.
On the days UK dogs were seen by a vet for heat-related illness, the median outdoor temperature was 16.9°C, about 62°F (Hall et al., Veterinary Sciences 2022).
That is not a heatwave. It is a pleasant spring afternoon.
While the hot car is the image every owner knows, it is not where most heatstroke happens. In the largest study of its kind, most cases followed exercise, and most of those followed a walk. This page sets out what the records show, which dogs are most at risk, the signs, and what the newest first-aid guideline says to do. Some of that guidance contradicts what owners have been told for years.
1. What the records show
A team from Nottingham Trent University and the Royal Veterinary College searched the records of 905,543 dogs seen at UK primary-care practices (Hall, Carter & O’Neill, Animals 2020). Where the trigger was recorded:
| Trigger | Share of events |
|---|---|
| Exercise | 74.2% |
| Hot weather, at rest | 12.9% |
| Shut in a vehicle | 5.2% |
Of the exercise cases with details, “372 (67.5%) occurred after walking”. Running, cycling, play and competitions made up the rest.
Exercise-triggered heatstroke was not milder. The odds of death after a hot car were similar to the odds after exercise. Because exercise cases were so much more common, “exertional HRI affected around ten times as many dogs and resulted in eight times as many deaths overall than vehicular HRI.”
The authors’ conclusion is the title of their paper, and the title of this page: “Campaigns to raise public awareness about heat-related illness in dogs need to highlight that dogs don’t die just in hot cars.”
Two more triggers worth knowing. Dogs shut in a hot building, for example when heating was left on or failed, had the highest odds of dying of any common trigger. And heatstroke during treatment at a vet or groomer was the fourth most common trigger with a known cause.
2. Which dogs are most at risk
The 2020 study found that “young male dogs had greater odds of exertional heat-related illness, older dogs and dogs with respiratory compromise had the greatest odds of environmental heat-related illness.” Flat-faced (brachycephalic) dogs had higher odds of all three main types.
The 2022 follow-up looked at which dogs died. “The risk of death in HRI cases was greater for those dogs with reduced capacity to thermoregulate (older and brachycephalic dogs).”
The 2026 RECOVER first-aid guidelines, from an international veterinary emergency initiative, summarise the risk factors: “higher body weight, higher body weight for breed/sex, brachycephalic conformation, and increasing age”. They add that “obesity has been associated with nonsurvival” (Mandell et al., Journal of Veterinary Emergency and Critical Care 2026).
The first warm days are the risky ones. RECOVER notes that cases “often increase in spring on some of the first warm days of the year”, possibly because dogs have not yet adjusted to the heat.
Our note: We say “flat-faced (brachycephalic)” rather than naming breeds, so as not to suggest other breeds are safe.
→ Choosing a Breed or a Mix: The Health Data Breeders Don’t Lead With
3. The signs
RECOVER lists the common signs of heat-related illness in dogs:
- constant panting
- sudden or unusual reluctance to play or keep going
- lying down unexpectedly during activity
- an anxious expression or restlessness
- seeming disoriented
- stumbling
- drooling heavily, vomiting, or diarrhoea
- collapse
It asks owners to keep “a high index of suspicion for heat‐related illness if they note any of these signs in high ambient temperatures or during physical activity.”
The hard case is the walk. RECOVER points out that owners recognise the danger in a hot car because they feel the heat themselves. On an exercise day, “Recognizing heat‐related injury in these circumstances may be more challenging if the bystander has a low index of suspicion.” A dog who lies down on a walk on a warm day is telling you something.
Heatstroke is an emergency. Any of these signs in heat or after exercise means cool first and go to a vet.
→ Emergency Signs in Dogs: When to Go Now, Not Tomorrow
4. Cool first, then go
This is the section where the advice has changed.
What the 2026 guidelines recommend. The RECOVER first-aid guidelines are direct: “we recommend active cooling on scene, if possible, before transport to a veterinary facility for definitive care, as long as the risk to the first aid provider is not high.” Their method:
- Stop the activity and move the dog somewhere cooler.
- Run cool water over the body, behind the neck, “with focus at an anatomic region with relatively less fur”, usually the belly, soaking down to the skin. Running water is better than a single bucket, because still water can form an insulating layer.
- Keep water away from the face, to avoid drowning.
- Don’t cool only the paws. The committee “does not recommend active cooling of dogs and cats by active cooling of only the paws.”
- If you can’t take your dog’s temperature, cool for about 15 minutes: “active cooling should be performed for 15 min prior to transport.”
- Pat your dog dry and go straight to a vet.
The guidelines also illustrate other ways to cool on scene, including submerging the body from the neck down in open water, or ice water from a cooler.
What happens in practice. A 2023 study of UK cases found that only 21.7% of dogs with a record of cooling were cooled before being taken to the vet. The most common method was wet towels, at 51.3%, which is not one of the methods the 2016 guidance recommended (Hall et al., Veterinary Sciences 2023). The authors call for “wider sharing of the advice to “cool first, transport second”.”
The cold-water warning. Many owners have read that you should never put a hot dog in cold water. The 2023 authors write that the advice to avoid cold-water immersion has persisted in medical and veterinary writing “Despite extensive evidence to the contrary”. RECOVER notes that human evidence does “not report harm or hypothermia associated with CWI or other active cooling techniques”, CWI meaning cold-water immersion.
To be fair to owners who are confused: the warning is still in reputable places. The Merck Veterinary Manual’s owner page on emergencies says “Do not immerse the animal in cold water” (Merck, What to Do in a Dog or Cat Emergency). We have followed the 2026 guidelines, which are newer and were written specifically for first aid.
Our note: This page follows the 2026 RECOVER guidance over Merck’s owner page.
Our note: RECOVER also gives a temperature at which to stop cooling. We give only the 15-minute rule, for owners who can’t take a temperature.
5. Preventing it
The studies point to where prevention matters most. We have kept to what they show, rather than the many rules of thumb that circulate.
- Treat walks as a risk, not just cars. Most cases followed exercise, and most of those followed a walk.
- Take the first warm days seriously. Cases rise in spring, before dogs have adjusted.
- Be most careful with flat-faced, older, heavier and overweight dogs. They are the dogs most likely to be affected, and the most likely to die.
- Stop at the first sign. RECOVER: “Working, running, playing, hiking, walking, or other activity should be stopped immediately.”
- Never leave a dog in a car, conservatory or closed room on a warm day. Shut-in dogs were the most likely to die.
Our note: We leave out pavement-temperature advice and walking thresholds, because they rest on human data.
6. What we could not verify
| Commonly said | What we found |
|---|---|
| “Heatstroke only happens on hot days” | Contradicted. The median outdoor temperature on UK heatstroke days was 16.9°C. |
| “Hot cars are the main danger” | Not in the UK records. Exercise triggered 74.2% of cases with a known trigger; vehicles 5.2%. |
| “Never use cold water on a hot dog” | Contradicted by the 2026 first-aid guidelines, which recommend cool running water and illustrate immersion. Merck’s owner page still says otherwise. |
| “Wet towels are the way to cool a dog” | Not a recommended method. They were the most common method used, but not one of the two the guidance recommends. |
| “The back-of-the-hand pavement test keeps paws safe” | We found no veterinary evidence for it. |
Sources
- Mandell DC, Thawley VJ, Burkitt-Creedon JM, Fletcher DJ, Boller M, Fausak E. RECOVER Guidelines: First Aid for Dogs and Cats. Clinical Guidelines. J Vet Emerg Crit Care 2026;S36–S62: consensus guideline; most heat-stroke recommendations are rated “expert opinion” or “very low” quality evidence. Funding acknowledged from Boehringer Ingelheim and Zoetis
- Hall EJ, Carter AJ, O’Neill DG. Animals 2020;10(8):1324: 905,543 UK dogs, VetCompass
- Hall EJ, Carter AJ, Chico G, et al. Vet Sci 2022;9(5):231: risk factors for severe and fatal cases
- Hall EJ, Carter AJ, Bradbury J, et al. Vet Sci 2023;10(7):465: cooling methods used, 2016–2018
- Merck Veterinary Manual: What to Do in a Dog or Cat Emergency (pet owner version)
Always confirm with your vet before acting on anything on this page.