Dogs don't cool down the way we do. They have very few sweat glands, and panting can only do so much once the air itself is hot and humid. That means a dog's body temperature can climb dangerously fast on a warm day — sometimes faster than owners expect, especially with flat-faced breeds, older dogs, puppies, overweight dogs, or dogs with heart or respiratory conditions. Knowing the early signs and the right first response can genuinely make the difference in an emergency.
Early Warning Signs to Watch For
Heatstroke rarely comes out of nowhere — there's usually a progression, and catching it early gives you more time to act. Watch for:
- Heavy, frantic panting that doesn't ease up with rest or water
- Bright red or purplish gums and tongue
- Thick, ropey drool
- Unsteadiness, stumbling, or reluctance to keep moving
- Vomiting or diarrhea
- Glassy eyes, disorientation, or collapse in more advanced cases
If you notice any of these during exercise, a car ride, or simply time spent outside on a hot day, stop what you're doing immediately and start cooling your dog down. Don't wait to see if it "passes" — heatstroke damage to organs can happen within minutes.
How to Cool Your Dog Down Safely
The instinct many people have is to grab the coldest water available, but that's actually one of the most important things to avoid. Extremely cold or ice water can cause the blood vessels near the skin to constrict, which traps heat inside the body's core instead of releasing it — and the shock of sudden extreme cold can also stress a dog that's already in crisis. We cover this in detail in our guide to why ice-cold water is the wrong tool for cooling an overheated dog, but the short version is: cool, not cold.
What to do instead
- Move your dog out of the heat immediately — into shade, an air-conditioned space, or at minimum out of direct sun.
- Wet their fur and skin with cool (room-temperature to lukewarm) water, focusing on the belly, inner thighs, armpits, and paw pads, where blood vessels sit close to the surface.
- Use a fan or air movement to help evaporative cooling do its work.
- Offer small amounts of cool water to drink if they're alert enough to swallow normally — don't force water into a dog who is disoriented.
- Call a vet or emergency clinic right away and head there, even if your dog seems to be improving. Heatstroke can cause internal effects that aren't visible from the outside, and a vet needs to check things like organ function and clotting that you simply can't assess at home.
Preventing Heatstroke in the First Place
Prevention is a lot less stressful than treatment. On hot or humid days, exercise dogs during the cooler parts of the morning or evening, always provide access to shade and fresh water, and never leave a dog in a parked car — even briefly (our guide to how fast cars heat up explains why "just a few minutes" is never actually safe). Watch pavement temperature too, since hot asphalt adds both burned paws and extra heat stress at the same time. Brachycephalic (flat-faced) breeds like bulldogs and pugs, senior dogs, and dogs carrying extra weight are at higher risk even in moderate heat, so it's worth being extra cautious with them and shortening outdoor time accordingly.
Why some dogs struggle more than others
Flat-faced breeds have a harder time panting efficiently because their airways are naturally more restricted, which limits how much heat they can release through breathing alone. Thick double-coated breeds, while often reasonably cold-tolerant, can also struggle in humid heat because their coat traps warmth against the skin. Overweight dogs carry extra insulation that works against them in hot weather, and dogs with underlying heart or lung conditions simply have less physiological reserve to draw on when their body is working overtime to cool itself. None of this means these dogs can't enjoy summer — it just means their safe window for exercise and outdoor time is genuinely shorter than a fit, short-nosed, moderate-coated adult dog's, and it's worth planning outings around that reality rather than a one-size-fits-all rule of thumb.
Humidity deserves its own mention here too, since it's easy to focus on the thermometer and forget it. Panting cools a dog through evaporation, and evaporation slows dramatically once the air is already saturated with moisture. That means a humid 82°F (28°C) day can be more dangerous for a dog than a dry 90°F (32°C) day, even though the number on the thermometer suggests otherwise — checking a combined heat index, where available, gives a more accurate picture than air temperature alone.
The Bottom Line
Heatstroke escalates quickly, but it's also one of the more preventable emergencies dogs face. Learn the early signs, know that cool (not ice-cold) water and shade are your first response, and always follow up with a vet visit even if your dog seems to bounce back — the safest habit is treating any suspected heatstroke as a true emergency rather than waiting to see how it plays out.