TL;DR: The warning signs of heatstroke in dogs are heavy non-stop panting, thick drool, a bright red tongue and gums, wobbliness, vomiting, and collapse. If you see them, move your dog to shade, pour cool water over the body, and get to a vet right away. Dogs cool by panting, not sweating, so they overheat far faster than people do, and heatstroke can turn deadly within minutes.
Heatstroke is one of the few dog emergencies where what you do in the first few minutes truly decides the outcome. The good news is that it is almost entirely preventable, and the signs are easy to spot once you know them. Here is what to watch for, and exactly what to do.
What are the signs of heatstroke in a dog?
Heatstroke builds in stages. The earlier you catch it, the better the outcome, so learn the mild signs, not just the scary ones.
Early signs (act now):
- Heavy, fast panting that does not slow down
- Thick, ropey drool or excess saliva
- A bright red tongue and gums
- Restlessness, or the opposite, slowing down and lagging behind
- Warm ears and body to the touch
Serious signs (emergency):
- Stumbling, wobbly legs, or disorientation
- Vomiting or diarrhoea, sometimes with blood
- Gums that turn pale, grey, or bluish
- Glazed eyes or a blank stare
- Seizures or collapse
Not every hot dog shows every sign, and the jump from early to serious can happen in minutes. When in doubt, treat it as heatstroke and start cooling.
How is heatstroke different from normal panting?
Panting is how a dog sheds heat, so panting after a walk or on a warm day is normal and healthy. The difference is whether it settles. Normal panting eases off within a few minutes of rest, water, and shade. Heatstroke panting is frantic, non-stop, and paired with the signs above.
If you often find yourself unsure, it is worth understanding why a dog pants so you can tell ordinary cooling from a red flag. A dog that keeps panting hard after ten minutes in the shade is telling you something.
What to do if your dog has heatstroke
Move fast and cool first. The steps below are the widely recommended first-aid response while you get help.
- Stop and move to a cool place. Get your dog into shade, indoors, or an air-conditioned car straight away.
- Cool with water. Pour, spray, or hose cool (not ice-cold) water over the whole body, focusing on the belly, armpits, groin, and paws. Ice-cold water can shrink surface blood vessels and slow cooling, so aim for cool tap temperature.
- Get air moving. A breeze, a fan, or an open window over wet fur speeds up cooling a lot.
- Offer small sips of water. Let your dog drink small amounts if it wants to. Do not force water into the mouth.
- Call the vet and go. Phone your vet or the nearest emergency clinic, tell them you are coming, and drive there while cooling continues. Keep the windows down or the AC on.
Stop active cooling once your dog is bright and comfortable again to avoid over-cooling, but still see the vet. Heatstroke can damage the kidneys, gut, and clotting system in ways that only show up hours later, even when a dog seems fine on the outside.
How hot is too hot for a dog?
A healthy dog's normal temperature sits around 38 to 39.2°C (101 to 102.5°F). Trouble starts near 40°C (104°F), and above 41°C (106°F) organ damage becomes likely. You do not need to take a temperature to act, but if you can safely, a reading over 40°C confirms an emergency. For the full picture, see what counts as a normal temperature for a dog.
How to prevent heatstroke
Prevention beats first aid every time. The big ones:
- Never leave a dog in a parked car. Even with windows cracked, the inside can hit lethal heat in 10 to 15 minutes. This is the single most common cause of fatal heatstroke.
- Walk and run at dawn or dusk. Skip midday heat, and check the ground with the back of your hand first. Our hot weather rules for running with your dog cover safe temperatures and the pavement test.
- Always carry water on warm-weather outings and offer it often, not just at the end. Watch for the early signs of dehydration in dogs, which often travel alongside overheating.
- Know your dog's risk. Flat-faced, overweight, very young, senior, and thick-coated dogs overheat sooner. Some breeds simply are not built for heat.
- Give shade and rest. On hot days, cut activity short and let your dog recover fully before going out again.
Watching the effort, not just the weather
Heatstroke often sneaks up on a keen dog that keeps going long after it should stop, because the drive to stay with you overrides its own sense of when to quit. That is why the safest owners watch the effort, not only the thermometer.
An activity tracker like Rocket shows how far and how hard your dog worked, so you can spot a big-effort day early and call the rest before your dog overheats. On warm days, treat a high activity reading as your cue to slow down, offer water, and head for shade. For more on keeping your dog fit and safe, browse our dog guides.