Heatstroke in dogs

As temperatures rise on warm spring days or during hot summer heatwaves your dog is more at risk of developing heatstroke (also known as heat-related illness, heat exhaustion, sunstroke or hyperthermia), but what causes it, how can you prevent it and what can you do to help treat an overheated dog?

What you need to know about heatstroke in dogs

Any dog can develop heatstroke, but some dogs, such as dogs that are large, energetic, overweight, have a thick coat or flat-faced, are more at risk than others. Heatstroke can occur at any time of the year, but often happens when people walk their dogs on hot summer days. It is important that owners know the signs of heatstroke (heavy panting, tiredness and dribbling) and should urgently contact their vet if they think their dog is affected. 1 in 7 dogs treated by vets for heatstroke die. To give a dog with heatstroke the best chance of survival they need to be cooled down immediately and taken to a vet as soon as possible.

What is heatstroke?

Heatstroke happens when a dog’s body can’t cope with an internal rise in temperature. Dogs are not as good at dealing with high temperatures as us and can only sweat to cool down on areas not covered by fur, such as their paws and nose. When they are hot, dogs mostly cool down by panting, but sometimes this just isn’t enough. As their body temperature rises it damages their tissues and organs, making them unwell. In severe cases, heatstroke can cause their organs to fail and can lead to death.

What causes heatstroke?

Heatstroke can be caused by a dog’s environment being too hot or by their muscles generating too much heat from exercise, or a mix of the two. Dogs are more at risk of developing heatstroke if they are without water, a good airflow or shade. Research has found that the common causes of heatstroke include:

  • Over-exercising, or exercising on hot days (around 75% of cases)
  • Not being able to cope in hot weather (around 13% of cases)
  • Being in a hot vehicle (around 5% of cases)
  • Being in a hot building (around 3% of cases)

Heatstroke most often occurs between May and August when the weather is warmer, but heatstroke from over-exercising can occur throughout the year. In very hot weather, even gentle exercise can lead to heatstroke, with nearly 70% of dogs with exercise induced heatstroke becoming unwell after just going for a walk on a hot day. Dogs that are not acclimatised to hot weather, such as during a heatwave, or those that have travelled from a cooler location to a warmer one, are more likely to be affected.

What are the signs of heatstroke?

Dogs usually keep their body temperature at around 37-39°C, but as their internal temperature rises, particularly above 41°C, they start to show signs of heatstroke. The hotter the dog becomes and the longer their temperature stays high, the more damaged their tissue and organs become.

Signs of heatstroke can progress quickly and can include:

  • Heavy panting, even when not exercising
  • Breathing problems, particularly in flat-faced dogs
  • Tiredness
  • Stiffness or an unwillingness to move
  • Dribbling
  • Confusion
  • Being sick, can be bloody
  • Upset stomach, can be bloody
  • Not walking in a straight line
  • Collapse
  • Fitting

If you think your dog may have heatstroke it is vital that you immediately contact your vet while cooling them down. Getting early advice and treatment is essential to saving a dog’s life. Research has found that in the UK, although 1 in 7 dogs that are taken to vets with heatstroke die, 98% that are seen early with mild signs are likely to survive.

How can I help treat a dog with heatstroke?

Any dog with heatstroke should be seen by a vet, particularly if they are very unwell or unconscious. If you don’t know where your closest vet is, you can find a vet near you here. It is important that you start to cool your dog as soon as possible - this can make a big difference to whether they survive.

Tips on how to help a dog with heatstroke:

  • Stop them exercising, move them out of the heat and into the shade
  • Call a vet for advice
  • Lay them down on a cool floor
  • Offer them small amounts of water to drink
  • Carefully pour water over the dog’s body, or sponge them if water is limited. Particularly focus on their neck, tummy and inner thighs. Ideally continue to do this until their breathing returns to normal. Make sure the dog doesn’t inhale any water while you’re trying to cool them down
  • Fan them with cool air or put them in an air-conditioned room or car if possible. The impact of fanning them, or putting them somewhere that’s air-conditioned, will be greatest if they’re already wet

It was previously thought that rapidly cooling an affected dog could cause them to go into shock. This advice is now being questioned, so always speak to your vet who can guide you through how best to help your dog.

When is it too hot for dogs?

Heatstroke can happen at any time of the year, but since some dogs are less able to cool themselves down it’s difficult to say which temperatures are safe. Most dogs are comfortable at temperatures between 15-25°C, but this is very much dependent on their age, breed, size, coat length, amount of exercise their engaging in, health and fitness. Some dogs may struggle to maintain a low body temperature, even in lower temperatures.

Which dogs are most at risk of heatstroke?

All dogs can develop heatstroke, but some dogs may be more at risk than others. Research has found that dogs with a higher chance of developing heatstroke include those that are:

  • Overweight
  • Flat-faced
  • More energetic
  • Older
  • Bigger, particularly those over 50kg
  • Have longer or thicker fur
  • Have health issues, including being dehydrated or having heart or breathing problems

Breeds at increased risk include: Chow Chows, Bulldogs, French Bulldogs, Dogue de Bordeauxs, Greyhounds, Boxers, English Springer Spaniels, Cavalier King Charles Spaniels, Pugs, Golden Retrievers and Staffordshire Bull Terriers. 

More energetic dogs may have a higher risk of heatstroke because they are physically more active, and the heat generated by their muscles can contribute to a rise in body temperature. Older dogs may be less active, but age-related health issues may make it harder for them to control their body temperature. Bigger dogs, overweight dogs and dogs with longer or thicker fur may retain body heat more easily and so may find it more difficult to cool down. Flat-faced dogs, such as Bulldogs, French Bulldogs and Pugs, may find it harder to lose heat from panting, because a shorter muzzle means a smaller surface area to cool them down.

Brachycephalic dogs, hot weather and overheating

Research has found that flat-faced dogs (brachycephalic dogs), are more than twice as likely to develop heatstroke when compared to dogs with a longer muzzle. Another study found that more than a third of owners of brachycephalic dogs thought that their dog struggled in hot weather. As dogs largely cool down by panting, a flat-faced dog’s narrower airways and shorter muzzle can affect their ability to cool down. This issue can be made worse if they already have breathing issues, such as BOAS (brachycephalic obstructive airway syndrome) or if they are overweight.

Some brachycephalic dogs seem to be at particular risk of overheating on hot days or in hot vehicles compared to other dogs. Extra care should be taken to keep your dog cool at home and on trips in the car.

Find out more about brachycephalic health issues or the work of the Brachycephalic Working Group, of which The Kennel Club is a member and read the Brachycephalic Working Group Consensus Statement on Preventing and Moderating Heat-related Illness in Dogs.

How long does heatstroke last?

If your dog has heatstroke you should immediately cool them down as you contact you vet for advice. Mild cases of heat related illness, where the owner has cooled the dog down and taken them to the vet urgently, are likely to make a full recovery quickly. However, if they have a serious case of heatstroke or treatment is delayed, they will need more intensive treatment that lasts for longer. 1 in 7 dogs that are treated for heatstroke will still die, so it is important to contact your vet if you think your dog is affected.

How can I help my dog stay cool in summer?

Keeping your dog cool on a hot day can help them feel more comfortable and reduces their risk of developing heatstroke. Below are some hints and tips to help you keep your dog safe.

When out walking

  • Exercise is the most common cause of heatstroke, so on hot days walk your dog in the early morning or evening and avoid the midday sun
  • Take extra care in heatwaves as your dog may not be acclimatised to warmer weather
  • Always carry water and something for your dog to drink from
  • Consider attaching a lead to a walking harness rather than to their collar. Leads that pull on a collar can press on their airways and stop them from cooling down as effectively. Remember that it’s a legal requirement for a dog to wear a collar with their owner’s name and address on when out and about
  • Take care when exercising any unwell or dehydrated dogs on hot or warm days as they may find it more difficult to control their body temperature
  • Owners and dog walkers should know the signs of heatstroke and watch out for them
  • Remember that pavements on hot days can burn your dog’s footpads, so try to avoid them. If it’s too painful for you to place the back of your hand on a pavement for seven seconds then it’s too painful for your dog to walk on. Find out more about the dangers of hot pavements

When travelling

  • Never leave your dog in the car by themselves
  • Make sure your dog has a safe, comfortable and cool spot in the car when you’re driving
  • Make regular stops to check on your dog and ensure they have access to water
  • Travel with cool water in a thermos to give to your dog
  • Avoid travelling during the hottest times of the day
  • Drive with the windows open or the air conditioning on
  • Use window sunshades to help reflect the sun’s rays and keep the car cooler when travelling
  • If using public transport, try not to travel on hot days or, if possible, check that the public transport you intend to use is air conditioned
  • Check that all places you want to visit are dog friendly so that you can take your dog in with you

At home

  • Avoid housing your dog in direct sunlight
  • Ensure your dog always has access to drinking water
  • Ensure your dog has a shaded space to keep them cool
  • Give your dog a paddling pool to splash around in
  • Add ice cubes to your dog’s water bowls
  • Freeze a dog toy and let your dog chew on it
  • Put down damp towels for your dog to lie on
  • If your dog has a long or heavy coat you could keep them clipped to make them feel more comfortable

The dangers of dogs in hot cars

Dogs die in hot cars. Even with the windows open, a car parked in the sun in the summer can quickly reach a temperature of over 50°C. Temperatures inside a car can soar, even if parked in the shade, and dogs can die in as little as 15 minutes. Although summer is a particular problem, temperatures in a car can become uncomfortable for some dogs all year round.

Find out more about the dangers of leaving your dog in the car.

Think your dog may be affected?

If you're worried about your dog's health, always contact your vet immediately.

We are not a veterinary organisation and so we can't give veterinary advice, but if you're worried about any of the issues raised in this article, please contact your local vet practice for further information.

Find a vet near you

If you're looking for a vet practice near you, why not visit the Royal College of Veterinary Surgeons' Find a vet page.