Pet Heatstroke in the UK: Signs, First Aid & Prevention

Quick Answer

Pet heatstroke happens when a dog or cat’s body temperature climbs above 39.5°C (103°F) and they can’t cool down fast enough, most often after exercise in warm weather, being left in a car, or restricted airflow in flat-faced breeds. It’s a genuine medical emergency: start cooling immediately with cool (not ice-cold) water, and get to a vet straight away even if your pet seems to recover, since internal damage can continue after outward symptoms ease.

Key Takeaways

• Heatstroke can set in within minutes, especially in cars, and is frequently fatal without fast action.
• Watch for heavy panting, drooling, wobbly legs, vomiting, bright red or purple gums, and collapse.
• Cool with room-temperature or cool water poured over the body, focusing on the neck, armpits and groin — avoid ice-cold water, which can restrict blood flow and make cooling less effective.
• Always see a vet after a suspected heatstroke episode, even if your pet appears to recover, as organ damage may not be immediately obvious.
• Flat-faced (brachycephalic) breeds, elderly pets, overweight animals and those with thick coats are at much higher risk.
• Never leave a dog in a parked car, even with windows cracked or parked in shade — UK car interiors can exceed 40°C within minutes on a mild day.

Why Trust This Guide?

This guide is researched and written by the Pets Store Home editorial team, drawing on published first-aid protocols and welfare guidance from established UK veterinary and animal welfare organisations, including the RSPCA, PDSA and Blue Cross. We focus on UK-specific context — climate, common breeds and typical summer risks — and review and update this content as guidance changes. This article is provided for general information and isn’t a substitute for veterinary advice; always contact a vet or emergency vet service if you suspect heatstroke.

Why UK Summers Catch Pet Owners Out

The UK doesn’t have a hot climate year-round, which is exactly why heatstroke catches so many pet owners off guard during a heatwave. Pets, especially dogs, can’t cool themselves down as efficiently as humans — they rely mainly on panting rather than sweating — so temperatures that feel manageable to us can be dangerous for them, especially in a car, a conservatory, greenhouse, or on a midday walk. This guide follows current guidance from the RSPCA and PDSA on recognising and responding to heat-related illness in pets.

Normal Temperature vs. Heatstroke: What’s Actually Happening

A dog’s normal body temperature sits between about 38.3–39.2°C (101–102.5°F). Once it climbs above roughly 39.5°C (103°F), a dog is entering heat stress; above 40°C (104°F) is considered a danger zone, and by 41°C (106°F) heatstroke is severe and potentially fatal — a rise of just a few degrees is the difference between discomfort and a life-threatening emergency. This is why heatstroke is treated as a genuine veterinary emergency rather than something to simply wait out at home.

Vets often describe a progression: heat stress (mild, resolves quickly with rest and water), heat exhaustion (more pronounced panting, weakness, but the pet is still responsive), and heatstroke (the body’s cooling mechanisms fail entirely, risking organ damage, seizures, and collapse). The earlier you intervene, the more likely a pet stays in the first stage rather than progressing to the last.

Signs of Heatstroke in Dogs and Cats

Watch for:

• Excessive or heavy panting
• Drooling that’s thicker or stickier than usual
• Confusion, disorientation, or a glazed look
• Vomiting or diarrhoea
• Muscle spasms or shivering despite the heat
• Breathing that’s noisier or faster than normal
• Red or unusually pale gums and tongue
• Weakness, wobbliness, or collapse

Cats show heatstroke less obviously than dogs, but the same core signs apply, along with agitation, unusual lethargy, or hiding away. Any of these signs during hot weather warrants immediate action, not a wait-and-see approach.

First Aid: Cool First, Transport Second

If you suspect heatstroke, the priority is to start cooling your pet down immediately, before you even think about getting to the vet. Move them to shade or somewhere cool, and pour or douse cool tap water (not ice-cold water) over their body — water at around 15–16°C works well. Avoid ice baths, ice packs, or iced water, as these can be counterproductive: they can cause blood vessels near the skin to constrict, trapping heat inside the body instead of releasing it.

Let your pet drink small amounts of cool water if they want to, and call your vet straight away to let them know you’re on your way, continuing to cool your pet as you travel. Heatstroke is a genuine emergency — always get a vet to check your pet even if they seem to recover once cooled, since internal damage (including kidney injury and clotting problems) can develop hours after the initial symptoms ease.

What Happens at the Vet

Once you arrive, a vet will typically continue active cooling in a controlled way, take a core temperature reading, and run bloodwork to check for early signs of organ stress, dehydration, or clotting problems, which are the main risks after a heatstroke episode. Pets with more severe cases are often kept in for intravenous fluids and monitoring for 24–48 hours, since some of the most serious complications don’t show up until a day or two later. This is exactly why a vet check is worth it even if your pet seems to bounce back quickly at home.

Preventing Heatstroke in the First Place

A few habits make the biggest difference:

• Walk dogs early in the morning or in the evening rather than during the hottest part of the day
• Check pavement temperature with the back of your hand — if it’s too hot for you to hold for five seconds, it’s too hot for paws
• Always provide shade and fresh, cool water, indoors and out
• Never leave a pet in a car, conservatory, greenhouse, or caravan, even briefly and even with a window cracked open
• Take extra care with flat-faced (brachycephalic) breeds like pugs, bulldogs, and Boston terriers, thick-coated breeds, very young or elderly pets, overweight pets, and any pet with an existing heart or respiratory condition

On the car point specifically: even on a mild-looking day, the inside of a parked car can climb by 10°C or more within just 10–15 minutes, so “just a couple of minutes” is never actually safe.

Don’t Forget Rabbits, Guinea Pigs, and Other Small Pets

Heatstroke advice tends to focus on dogs, but rabbits and guinea pigs are just as vulnerable, particularly if they’re kept in an outdoor hutch. Make sure hutches and runs are somewhere shaded — and remember that shade moves with the sun through the day, so a spot that’s shaded in the morning may be in full sun by the afternoon. Never house rabbits or guinea pigs in a greenhouse or conservatory. A simple trick many UK owners use is to freeze a plastic bottle of water, wrap it in a towel, and leave it in the enclosure so the animal can lie against it to cool down.

If you suspect a rabbit or guinea pig has heatstroke, move them to a cool, shaded spot, wrap them in a cool, damp towel (not ice-cold), and call your vet immediately — heatstroke in small pets can progress very quickly.

Heatstroke in Cats: A Closer Look

Cats are often left out of heatstroke advice because they’re generally better than dogs at avoiding heat — they seek shade instinctively and are less likely to be dragged out for a midday walk. But indoor cats, especially those without easy access to a cool room, a flat with a hot conservatory, or a cat carrier left in a warm car or on a train platform, are still at real risk.

Cats tend to hide signs of illness rather than show obvious distress, so heatstroke in cats can be easy to miss until it’s advanced. Beyond the general signs already covered, watch for a cat that’s unusually still and unresponsive, stretched out flat in an attempt to lose heat, or breathing through an open mouth — open-mouth breathing is normal for an overheated dog but is a much more worrying sign in a cat, since cats don’t pant as a first response the way dogs do.

Exercise and Exertional Heatstroke

Not all heatstroke happens because a dog was left somewhere hot — a lot of cases develop during exercise, even in dogs that are otherwise fit and healthy. A game of fetch, an agility session, or a longer run on a warm, humid morning can push a dog’s temperature into the danger zone faster than owners expect, particularly if the dog is motivated to keep going and doesn’t self-regulate.

Working and sporting breeds are especially prone to this because they’re bred to keep pushing through discomfort. If you’re exercising a dog in warm weather, build in regular breaks in shade, offer water often rather than waiting until the end, and watch for early signs of slowing down, seeking shade unprompted, or reluctance to continue — these are the moments to stop, not power through.

Why Humidity Makes Heat More Dangerous

Temperature alone doesn’t tell the whole story. Dogs cool down mainly by panting, which relies on evaporation — moisture leaving the tongue and airways carries heat away with it. In humid air, that evaporation slows down dramatically, because the surrounding air is already close to saturated with moisture and can’t absorb much more.

This is why a warm, muggy day with high humidity can be more dangerous for a dog than a hotter but drier day. If you’re checking a weather forecast before a walk, it’s worth glancing at the humidity percentage alongside the temperature, not just the temperature on its own.

Recovery and Aftercare at Home

Once your vet is satisfied your pet is stable and safe to go home, recovery isn’t necessarily over. Follow any specific instructions from your vet, but general aftercare usually includes rest for several days, easy access to water, a cool environment, and a noticeably reduced exercise routine while the body recovers.

Keep an eye out for reduced appetite, lethargy that doesn’t improve, unusual urination (more, less, or a different colour than normal), or vomiting in the days after a heatstroke episode — these can be signs of the delayed organ complications mentioned earlier, and are worth a follow-up call to your vet rather than waiting to see if they pass on their own.

Breed-by-Breed Risk: A Closer Look

Some risk factors are well known, but it’s worth understanding why they matter:

• Flat-faced (brachycephalic) breeds — pugs, bulldogs, French bulldogs, Boston terriers, and Persian cats have shortened airways that make panting, their main cooling method, far less effective.
• Thick-coated and double-coated breeds — huskies, malamutes, and Bernese mountain dogs are built to retain heat, which is a disadvantage once the temperature climbs.
• Giant breeds — larger dogs generate more body heat relative to their surface area, making it harder for them to dump that heat quickly.
• Dark-coated animals — darker fur and skin absorb more heat from direct sunlight than lighter colouring.
• Very young, elderly, overweight pets, or those with heart or respiratory conditions — all have reduced capacity to regulate temperature efficiently, for different underlying reasons.

None of this means these pets can’t enjoy summer — it just means their owners need a slightly lower threshold for caution than owners of, say, a lean, short-coated, middle-aged dog.

Common Heatstroke Myths, Debunked

“It only happens in cars.” Cars are a well-known danger, but plenty of heatstroke cases happen on ordinary walks, in gardens without shade, or during exercise — the car is just the most publicised scenario, not the only one.

“Shaving a thick-coated dog keeps them cooler.” Not necessarily. A dog’s coat can help regulate temperature and protect against sunburn; shaving it doesn’t always help and can sometimes do more harm than good. If you’re considering it, a groomer or vet familiar with your dog’s coat type is a better source of advice than a general assumption.

“My dog will stop on their own before it’s dangerous.” Some dogs, especially working and sporting breeds, will keep going well past the point where they should stop, because drive and instinct can override the signals that would normally make them rest.

“Only old or unhealthy pets are at risk.” Age and health both matter, but fit, young, healthy pets can and do get heatstroke, particularly during exercise or if left somewhere hot even briefly.

Travelling and Days Out Safely in Hot Weather

Heatstroke risk doesn’t stop once you’re out of the car. On a hot day out — a beach trip, a country show, a festival, or a long train journey — plan for shade and water at every stage, not just at the destination. Carry a collapsible water bowl, check whether your destination genuinely has shaded areas rather than assuming it will, and avoid busy midday hours if the itinerary is flexible.

For train and public transport travel, carriages and platforms can get surprisingly warm, and pets in carriers have less ability to move to a cooler spot than pets on a lead. Where possible, travel outside of peak heat hours, and never leave a pet in a stationary vehicle or unattended luggage area, even for what feels like a quick errand.

Hydration and Electrolytes: What Actually Helps

Fresh, cool water is the main thing that matters — most pets don’t need anything more elaborate than that on a hot day. Some owners ask about electrolyte solutions or sports drinks made for humans; these aren’t generally recommended for pets, since they’re formulated for human physiology and can contain sugar or additives that aren’t appropriate. If your vet recommends an oral rehydration solution as part of recovery from heat-related illness, they’ll typically suggest a pet-specific product rather than something from a human sports aisle.

What helps more in practice is making water genuinely easy to access: multiple bowls around the house and garden, a bowl that’s topped up rather than left low, and for cats in particular, a bowl kept away from food (many cats prefer this) and refreshed often, since some cats drink more readily from moving or very fresh water.

Special Considerations for Puppies and Senior Pets

Puppies and senior pets sit at opposite ends of the age range but share a similar vulnerability: their bodies are less able to regulate temperature efficiently than a fit adult pet. Puppies have less developed thermoregulation and often haven’t yet learned to pace themselves during play, while senior pets frequently have some degree of reduced heart or lung function, even if it hasn’t been formally diagnosed, which limits how well they can cope with heat stress.

For both groups, the practical advice is the same: shorter, more frequent outings rather than one long walk, closer supervision during play or exercise in warm weather, and a lower threshold for calling it a day at the first sign of tiredness, heavy panting, or reluctance to keep moving.

FAQ: Pet Heatstroke in the UK

Should I use ice or ice-cold water to cool my pet down?
No. Ice baths and ice-cold water can constrict blood vessels near the skin and trap heat inside, making cooling less effective. Cool tap water (around 15–16°C), poured or doused over the body, works better and is safer.

What’s the difference between heat exhaustion and heatstroke?
Heat exhaustion means a pet is overheated but still responsive — heavy panting, weakness, but alert. Heatstroke is more severe: body temperature climbs into the danger zone (above roughly 40°C/104°F), and the body’s cooling mechanisms start to fail, risking organ damage and collapse. Heatstroke always needs emergency vet care.

Do I still need to see a vet if my pet seems fine after cooling down?
Yes. Heatstroke can cause internal damage, including kidney and clotting problems, that isn’t obvious once the initial symptoms ease and can take a day or two to appear, so it’s always worth having a vet check your pet after a suspected episode.

Which pets are most at risk of heatstroke?
Flat-faced breeds, thick-coated breeds, very young or elderly pets, overweight pets, and pets with existing heart or breathing conditions are all at higher risk, even in moderate UK summer temperatures. Rabbits and guinea pigs in outdoor hutches are also at real risk and are often overlooked.

Can rabbits get heatstroke?
Yes, and it can progress quickly. Keep hutches shaded (shade moves through the day, so check more than once), never house rabbits in a greenhouse or conservatory, and provide a frozen water bottle wrapped in a towel for them to lie against on hot days.

How hot does it need to be for a car to become dangerous for a pet?
Even on a mild day, the inside of a parked car can climb by 10°C or more within 10–15 minutes, so pets should never be left in a car, even briefly or with a window cracked open.