Signs of Heatstroke in a Dog and What to Do

At a glance

• Heatstroke occurs when a dog's core body temperature rises above 40°C (104°F)
• Early signs include heavy panting, excessive drooling, and bright red or pale gums
• Severe heatstroke can cause seizures, collapse, and organ failure within minutes
• Cool the dog gradually with cool (not ice cold) water — never use ice
• Heatstroke is fatal in around 50% of severe cases — speed of treatment is everything

What does heatstroke in a dog actually look like?

Heatstroke happens when a dog's body overheats and can no longer regulate its own temperature. Unlike humans, dogs cool themselves almost entirely through panting. When the surrounding temperature overwhelms that system, their core temperature climbs rapidly — and organs start to fail.

A dog's normal body temperature sits between 38°C and 39.2°C. Once it reaches 40°C, heatstroke begins. Above 41.5°C, cell damage accelerates fast. At 43°C, survival without immediate veterinary intervention is unlikely.

The early signs are easy to miss because some of them look like normal warm-weather behaviour. Knowing what to look for at each stage is the difference between a close call and a tragedy. Heatstroke in dogs progresses in stages, and understanding how common conditions escalate helps you act before it becomes critical.

What are the signs of heatstroke in dogs?

Heatstroke signs range from subtle to severe. They tend to develop quickly, often within 15 to 30 minutes of exposure to excessive heat.

Early signs:

• Heavy, rapid panting — much more intense than normal
• Excessive drooling or thick, stringy saliva
• Bright red gums and tongue
• Restlessness or agitation
• Seeking shade or cool surfaces

Moderate signs:

• Weakness or wobbling when walking
• Vomiting or diarrhoea
• Eyes appearing glazed or unfocused
• Skin inside the ears becoming flushed and hot

Severe signs:

• Collapse or inability to stand
• Seizures or muscle tremors
• Gums turning pale, blue, or grey
• Loss of consciousness

If you see any moderate or severe signs, treat this as a veterinary emergency. Do not wait to see if your dog improves on their own.

Which dogs are most at risk of heatstroke?

Every dog can get heatstroke, but some are significantly more vulnerable than others.

Brachycephalic breeds — flat-faced dogs such as Bulldogs, Pugs, French Bulldogs, and Boxers — are at highest risk. Their restricted airways make panting far less efficient. Studies show brachycephalic dogs are over 14 times more likely to suffer heatstroke than longer-nosed breeds.

Other high-risk groups include:

• Overweight or obese dogs — excess body fat retains heat
• Senior dogs and puppies — less efficient at regulating temperature
• Double-coated or thick-coated breeds such as Huskies and Chow Chows
• Dogs with heart or respiratory conditions
• Any dog left in a car, even on a mild day — the temperature inside a parked car can reach 47°C within 60 minutes on a 22°C day

If your dog falls into any of these categories, take extra precautions during warm weather. Walk in the early morning or after 6pm, always carry water, and avoid hot pavements.

What should you do if your dog has heatstroke?

Act immediately. Every minute counts. Here is the correct sequence:

1. Move them to a cool place. Get your dog out of the sun and into shade or an air-conditioned space right away.

2. Apply cool water. Use cool (not ice cold) water over the body, focusing on the neck, armpits, groin, and paws. These areas have large blood vessels close to the surface. A wet towel draped over the dog is effective — but do not wrap it tightly, as this traps heat.

3. Do not use ice or very cold water. Ice causes blood vessels near the skin to constrict. This prevents heat from escaping the body's core and can make things worse, not better.

4. Encourage small sips of cool water if your dog is conscious and able to swallow. Never force water into an unconscious dog.

5. Call your vet immediately. Even if your dog appears to be recovering, internal damage — including to the kidneys, liver, and brain — can occur without obvious external signs. A vet needs to assess your dog as soon as possible. This is one situation where waiting and watching at home is never the right call.

Cooling should continue during transport. Keep windows open and the air conditioning on. Place a wet towel under your dog on the back seat.

How does diet and overall health affect a dog's resilience to heat?

Heatstroke is not a nutrition issue — no food prevents it. But a dog's overall health directly affects how well their body copes with stress, including heat. Dogs carrying excess weight struggle more in hot weather, as fat acts as insulation and puts additional strain on the heart. Keeping your dog at a healthy weight through appropriate feeding is one of the most practical things you can do for their long-term resilience.

Hydration matters year-round, but especially in summer. Dogs eating fresh food get a proportion of their fluid intake through their meals — fresh diets typically contain 70 to 80% moisture compared to as little as 10% in dry kibble. Marleybones Pantry Fresh meals are freshly prepared with no artificial preservatives, making them a straightforward way to support daily hydration alongside a fresh water supply.

Every dog is different — build your personalised Marleybones feeding and health plan tailored to your dog's age, size, and health requirements.

If your dog is overweight and you want to understand more about managing their condition through diet, the right food choices can make a meaningful difference to their weight and overall health.

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FAQs

Can a dog get heatstroke indoors?

Yes. Heatstroke does not require direct sunlight. A hot, poorly ventilated room is enough to cause dangerous overheating — particularly in flat-faced breeds or dogs left without water. Always ensure dogs have access to shade, airflow, and fresh water indoors during warm weather.

How long does it take for a dog to get heatstroke?

In extreme conditions, heatstroke can develop within 15 minutes. A dog left in a parked car on a warm day is at serious risk in under 30 minutes. Signs escalate quickly, so early intervention is critical.

Should I take my dog to the vet even if they seem to recover?

Yes, always. Internal organ damage from heatstroke is not always visible immediately. Kidney failure and other complications can develop hours after a dog appears to have cooled down. A vet assessment after any suspected heatstroke episode is essential.

What temperature is too hot to walk a dog?

As a general rule, if the pavement is too hot to hold your hand on for 7 seconds, it is too hot for your dog's paws. In the UK, temperatures above 25°C carry a meaningful risk for most dogs. Walk in the early morning or evening and keep sessions short on hot days.

Is heatstroke the same as heat exhaustion in dogs?

Heat exhaustion is the stage before full heatstroke. It involves heavy panting, weakness, and discomfort but the dog is still conscious and responsive. Heatstroke is the more severe state — body temperature is critically elevated and organ damage is occurring. Both require urgent action, but heatstroke is the more dangerous emergency.

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