Dr. Tiffany Delacruz, DVM • Chief Executive Officer, RexVet • 2026-06-06 • 9 min read
Dog Heatstroke: Warning Signs, First Aid, and When It's a Vet Emergency
Heatstroke kills dogs in minutes, not hours. Here is what a licensed veterinarian wants every pet owner to know going into summer: the early warning signs most people miss, the exact first-aid steps, and the temperature threshold that means call an emergency vet now.
Medically reviewed by Dr. Tiffany Delacruz, DVM
Heatstroke is one of the few veterinary emergencies where the difference between full recovery and death is measured in minutes. Every summer, RexVet's licensed veterinarians take calls from panicked pet parents whose dog was 'fine an hour ago.' Most of those dogs survive when the family acts fast. The ones that do not survive almost always involved a delayed call — waiting to see if the dog would 'sleep it off.' This guide covers what every dog owner should know before the next hot day.
What heatstroke actually is
Dogs do not sweat the way humans do. They thermoregulate primarily by panting, with a small contribution from sweat glands in the paw pads. When ambient temperature, humidity, exertion, or all three exceed the dog's ability to dissipate heat, core body temperature rises above the normal range (101-102.5°F for most dogs). Above 104°F is hyperthermia. Above 106°F is heatstroke, which damages cells throughout the body — brain, kidneys, liver, intestinal lining, and clotting system. Once the cascade starts, every minute matters.
The warning signs — early, mid, and late
Most pet owners only recognize the late signs, by which point the dog needs an emergency clinic immediately. Learn the early ones.
Early signs (act now)
These mean stop the activity, get into shade and air conditioning, and offer water:
- Heavy, fast panting with a wide, flat tongue
- Drooling — more than usual, often thick and ropey
- Bright red gums and tongue (compared to the dog's normal pink)
- Restlessness or refusing to keep walking
- Glassy or distant-looking eyes
Mid signs (drive to emergency vet)
These mean the situation is escalating fast. Do first aid and get on the road:
- Vomiting or diarrhea (sometimes bloody)
- Weakness, wobbling, or trouble standing
- Confusion or unresponsiveness to name
- Dark red or purple gums
- Rectal temperature above 104°F if you have a thermometer
Late signs (true emergency — call ahead)
These mean call the emergency clinic from the car so they are ready when you arrive:
- Seizure activity
- Collapse or inability to stand
- Loss of consciousness
- Bloody vomit or diarrhea
- Very pale, white, or blue gums
First aid: the exact steps
If you suspect heatstroke, do these steps in this order. Do not skip the emergency clinic visit even if your dog seems better — internal organ damage from heatstroke can present 12-48 hours later and is often fatal without supportive care.
Cool water, not ice water
Move the dog to shade or air conditioning. Wet them with cool tap water — focus on the belly, armpits, groin, and paws where blood vessels are close to the surface. Do not use ice water or ice packs: dramatic cold causes peripheral blood vessels to constrict, which traps heat in the core and makes the problem worse.
Airflow accelerates evaporation
Point a fan at the wet dog, or roll down the car windows on the way to the clinic. Evaporative cooling is faster than water alone.
Offer water but do not force it
If the dog is alert and willing, let them drink small amounts of cool water. Do not pour water down their throat — vomiting or aspiration during heatstroke can be deadly.
Drive to the nearest 24-hour emergency clinic
Even mild heatstroke needs veterinary evaluation. The clinic will check core temperature, monitor for organ damage, run baseline bloodwork, and start IV fluids if indicated. A telehealth visit cannot substitute for in-person heatstroke care.
Who is highest risk
Some dogs are at dramatically higher risk than others, and pet parents in those categories should adjust summer routines proactively.
- Brachycephalic (flat-faced) breeds: Bulldogs, French Bulldogs, Pugs, Boxers, Boston Terriers, Cavalier King Charles Spaniels. Their shortened airways make panting far less effective.
- Senior dogs (over 7-10 depending on breed)
- Overweight or obese dogs
- Dogs with heart disease, respiratory disease, or laryngeal paralysis
- Thick double-coated breeds: Huskies, Malamutes, Bernese Mountain Dogs, Newfoundlands
- Puppies under 6 months — their thermoregulation system is still developing
Prevention is the entire game
Prevention is dramatically easier than treatment. A few rules that have prevented every heatstroke case we have seen at RexVet from happening twice:
Never leave a dog in a parked car
On a 75°F day, the interior of a parked car reaches 100°F within 10 minutes and 120°F within 30 minutes — even with windows cracked. This is not a debate. It is the single most common cause of fatal heatstroke we see every summer.
Walk on grass, not pavement
Asphalt and concrete absorb heat. At 87°F ambient, asphalt can reach 140°F — hot enough to burn paw pads in 30 seconds. Test with the back of your hand: if you cannot hold it on the pavement for 7 seconds, it is too hot for your dog.
Walk early or late
Shift walks to before 8 AM or after 7 PM during heat waves. Skip walks entirely on days when the heat index is over 95°F, especially for high-risk breeds.
Provide constant fresh water and shade
Indoors and outdoors. For outdoor time, a kiddie pool with shallow water is one of the most effective cooling tools you can buy for a dog.
Step-by-step
Dog Heatstroke First Aid: The Exact Steps
What to do in the first 5 minutes if you suspect your dog has heatstroke — step-by-step first aid from a licensed veterinarian.
Move to shade and stop activity immediately
Get the dog into shade or air conditioning. Stop walking, running, or any exertion. Lay them down on a cool surface.
Apply cool water to high-blood-flow areas
Wet the belly, armpits, groin, and paw pads with cool — NOT ice-cold — tap water. Ice water causes blood vessels to constrict and traps heat in the core.
Add airflow to accelerate evaporation
Point a fan at the wet dog, or in the car, open the windows. Evaporative cooling works faster than water alone.
Offer small amounts of cool water if alert
If the dog is conscious and willing, let them drink small sips. Never force water — it risks aspiration during heatstroke.
Drive to the nearest 24-hour emergency clinic
Even if the dog seems better, internal organ damage can present 12-48 hours later. Call ahead so the clinic is ready.
Emergency signals
When to contact a veterinarian
- Suspected heatstroke — go to the nearest 24-hour emergency clinic immediately
- Rectal temperature above 104°F
- Bright red or very pale gums
- Vomiting, diarrhea, or collapse after heat exposure
- Seizure or loss of consciousness
- A flat-faced breed showing any signs of respiratory distress in heat
Frequently asked questions
What temperature is dangerous for dogs?
There is no single safe temperature — it depends on breed, age, weight, humidity, and exertion level. As a general rule, exercise caution above 80°F for any dog, above 75°F for brachycephalic (flat-faced) breeds and senior or overweight dogs, and avoid prolonged outdoor exposure above 90°F for any dog.
How long does it take for a dog to get heatstroke in a car?
On a 75°F day, a parked car can reach 100°F within 10 minutes and 120°F within 30 minutes, even with windows cracked. Heatstroke can begin within 15-30 minutes in those conditions. Never leave a dog in a parked car in warm weather.
Is my dog panting heavily or is this heatstroke?
Normal hot-day panting is fast but rhythmic, the tongue is normal pink, and the dog responds normally. Heatstroke panting is heavy, often with a wide flat tongue, bright red gums and tongue, thick drool, and reduced responsiveness. If you are unsure, treat it as an emergency — the cost of being wrong is much higher in one direction than the other.
Can I treat heatstroke at home without a vet?
No. Even mild heatstroke can cause organ damage that presents hours later. Cool the dog with first aid, then drive directly to a 24-hour emergency clinic. Telehealth can guide you through first aid in the moment, but cannot substitute for in-person evaluation, IV fluids, and bloodwork.
Why is ice water bad for an overheating dog?
Ice water and ice packs cause peripheral blood vessels (the ones near the skin) to constrict. That traps heat in the core where the organs are, making the heatstroke worse. Cool tap water on the belly, armpits, groin, and paws cools blood gently as it circulates through those high-blood-flow areas.
Are flat-faced breeds really at higher risk for heatstroke?
Yes — significantly. Bulldogs, French Bulldogs, Pugs, Boxers, and similar brachycephalic breeds have shortened airways that make panting (the dog's primary cooling mechanism) far less effective. They overheat faster, cool down slower, and have a documented higher rate of fatal heatstroke. Adjust summer routines accordingly.