Heatstroke in dogs progresses fast and is frequently fatal. It also does not require extreme weather — a mild, humid day and a moderately enthusiastic dog are quite sufficient.
Most cases are not dogs left in cars. The commonest cause is exercise: a walk, a game of fetch, a run alongside a bike on a day that felt fine to the person holding the lead.
Why dogs overheat so easily
Dogs barely sweat. They lose heat mainly by panting, which moves air over wet surfaces in the mouth and airway. That works well in dry air and poorly in humid air, which is why a muggy 24°C day can be more dangerous than a dry 30°C one.
They also have no sense of pacing themselves. A dog chasing a ball will keep chasing it past the point where their body can cope.
The dogs most at risk
- **Flat-faced breeds** — bulldogs, French bulldogs, pugs, boxers. Their airways are far less efficient at cooling, and they are dramatically over-represented in heatstroke cases.
- **Overweight dogs**
- **Thick double-coated breeds** — huskies, malamutes, German shepherds
- **Very young and very old dogs**
- **Dogs with heart or airway disease**
- **Black-coated dogs** in direct sun
What it looks like
Early:
- Heavy, fast panting that does not slow with rest
- Very red gums and tongue
- Thick, ropey drool
- Seeking shade, slowing, lagging behind
Serious — this is an emergency:
- Wobbliness, stumbling, weakness
- Vomiting or diarrhoea, sometimes bloody
- Confusion, glazed expression, unresponsiveness
- Gums that look pale, grey or blue
- Collapse or seizures
What to do
- **Stop everything** and get the dog out of the sun, into shade or indoors.
- **Cool them with water, now.** Current veterinary emergency guidance favours cooling aggressively — pour or douse cool water over the whole body, or immerse them if you safely can. The old advice to use only tepid water and avoid cold has been revised; the priority is bringing the temperature down fast.
- **Move air over them** — a fan, an open car window, anything.
- **Offer small amounts of water** to drink if they are conscious and able. Do not force it.
- **Phone the vet and go**, continuing to cool on the way. Keep the car windows open or the air conditioning on hard.
- **Do not cover them** with wet towels and leave them. A wet towel left in place traps heat. Keep re-wetting and keep air moving.
Even a dog who appears to recover needs seeing. Heatstroke can cause organ damage and clotting problems that appear hours later.
Prevention, which is the real answer
**Walk early or late.** Before seven in the morning, after eight in the evening in hot weather.
**Use the hand test on pavement.** Press the back of your hand to the surface for seven seconds. If you cannot hold it there, it is too hot for paws — and if the ground is that hot, the air above it is worse.
**Cancel the walk.** A dog missing one walk is fine. Do enrichment indoors instead — a food puzzle or a scatter feed in the shade tires them out without heat.
**Never leave a dog in a car.** Not with the windows cracked, not in the shade, not “for two minutes”. Car interiors climb astonishingly fast.
**Watch the humidity**, not just the temperature.
**Do not shave a double coat.** It insulates against heat as well as cold, and shaving can make things worse as well as damaging regrowth. Brush out the dead undercoat instead.
**Carry water** on every summer walk.
Cooling equipment
Cooling mats and cooling coats can help, but they are supplements to shade, water and sensible timing, not replacements. A cooling coat on a dog being exercised in midday sun is still a dog being exercised in midday sun.
The honest summary
Dogs die of heatstroke on ordinary summer days, usually while exercising, usually with an owner who did not think it was that hot.
Walk early, use the pavement test, cancel when in doubt, and if it happens — cool first, phone while cooling, and go.
