Heatstroke in Dogs: Warning Signs and How to Prevent It
Heatstroke in dogs is a life-threatening emergency. Learn the warning signs, what to do straight away and simple ways to prevent overheating.
By Matt, founder · 21 May 2026 · Lived-experience guidance, not medical advice.
Heatstroke in dogs is a genuine, fast-moving emergency, and recognising it early saves lives. The key signs are heavy, frantic panting, drooling, bright red gums, lethargy or collapse, and vomiting; if you see these, you need to cool your dog and contact a vet immediately. Prevention is far easier than treatment: avoid heat at peak times, never leave a dog in a car, and give them ways to cool down.
UK summers are getting hotter, and dogs cope with heat far worse than we do. Here's what to watch for and how to keep your dog safe.
Know the warning signs
Dogs don't sweat through their skin the way we do; they cool mainly by panting, which becomes overwhelmed quickly. Early to advanced signs include:
- Excessive, heavy panting that doesn't settle
- Drooling, sometimes thick and sticky
- Bright red or dark gums and tongue
- Lethargy, stumbling or weakness
- Vomiting or diarrhoea
- Collapse, seizures or unresponsiveness in severe cases
Heatstroke can escalate within minutes. If your dog shows more than mild, settling panting on a warm day, treat it seriously.
What to do if you suspect heatstroke
Act fast and cool first, then call the vet on the way:
1. Move your dog to shade or a cool, ventilated spot immediately. 2. Pour or spray cool (not ice-cold) water over them, focusing on the body, neck, belly and paws. Recent veterinary guidance favours active cooling with cool water straight away, including pouring water over the dog, rather than waiting. 3. Keep air moving with a fan or open window to help evaporation. 4. Offer small amounts of cool water to drink if they're conscious and willing; don't force it. 5. Call your vet or the nearest emergency vet now and head there. Tell them you're coming. Dogs can deteriorate even after they seem to recover, so a vet check is essential.
Avoid ice-cold water or ice baths, which can constrict blood vessels and slow cooling. Cool, not freezing, is the rule.
Who's most at risk
Some dogs overheat far more easily:
- Flat-faced (brachycephalic) breeds like Bulldogs, Pugs and French Bulldogs, whose airways make panting inefficient
- Overweight dogs and double-coated or thick-coated breeds
- Puppies, senior dogs and those with heart or breathing conditions
- Dark-coated dogs that absorb more heat
If your dog falls into one of these groups, be especially cautious in warm weather.
Preventing heatstroke
Most cases are entirely avoidable with a few habits:
- Walk early or late. Avoid the hottest part of the day, roughly late morning to late afternoon in a UK heatwave. On very hot days, skip the walk altogether; a missed walk never hurt a dog, but heatstroke can kill.
- Never leave a dog in a car, not even briefly with windows cracked. Cars become ovens within minutes, even on a mildly warm day.
- Check the pavement. Hot tarmac burns paws. Our hot pavement and burnt paws guide explains the simple seven-second test before you set off.
- Provide shade and fresh water at all times, indoors and out.
- Use cooling aids. A dog cooling mat gives your dog a cool surface to lie on indoors, and a dog cooling vest helps on warm-weather outings. See our best dog cooling mats round-up for specific picks.
- Freeze treats and use a paddling pool for active dogs who need to burn energy without overheating.
During a heatwave
Keep the house cool with closed curtains during the day, leave water in several spots, and watch your dog for the first signs of distress. Avoid car travel in the heat unless air conditioning is reliable. If you're exercising at all, keep it gentle and brief, and stop the moment panting becomes heavy.
A vet check is wise even after a near-miss, because internal effects of overheating aren't always visible.
The bottom line
Heatstroke is fast, frightening and often fatal, but it's also one of the most preventable emergencies in dogs. Walk in the cool, never leave a dog in a car, provide shade, water and cooling, and know the signs so you can act instantly. Explore more warm-weather advice in our seasonal pet care hub, and find cooling kit in our health and grooming shop.
Common questions
What are the first signs of heatstroke in a dog?
The earliest signs are heavy, frantic panting that won't settle, excessive drooling and bright red gums. As it worsens you may see lethargy, stumbling, vomiting and eventually collapse. Any of these on a warm day should be treated as an emergency.
Should I use ice-cold water to cool an overheating dog?
Use cool water rather than ice-cold. Pour or spray cool water over the body, neck, belly and paws and keep air moving with a fan. Ice-cold water or ice baths can constrict blood vessels and actually slow cooling, so cool, not freezing, is the safest approach while you head to the vet.
At what temperature is it too hot to walk a dog?
There's no single cut-off, as it depends on the breed, age and humidity, but caution rises sharply once it's into the low-to-mid twenties Celsius, and flat-faced or overweight dogs struggle sooner. Walk early or late, do the seven-second pavement test, and skip the walk entirely on very hot days.
Can a dog die from being left in a car?
Yes. A car heats up rapidly even on a mildly warm day, and even with windows cracked it can reach lethal temperatures within minutes. Never leave a dog in a parked car, however brief the errand. If you see a dog in distress in a car, call 999.
About the author
Matt — founder, Everypaw Supply Co
Matt started Everypaw Supply Co to make getting pets the good stuff simpler and fairer. Everything in these guides comes from real life with pets and a lot of trial and error — it's practical guidance, not veterinary advice. If a guide gets something wrong, tell him directly.