Dogs cool almost entirely by panting, which works by evaporating water from the airways. It is far less efficient than sweating, and it stops working when the air is hot and humid.
That is why heatstroke can develop within minutes, and why it kills. Reported mortality rates in severe cases are high even with prompt veterinary treatment.
Most cases are not dogs in cars. They are dogs on walks.
The pavement test
Press the back of your hand flat against the pavement and hold it for seven seconds.
If you cannot keep it there comfortably, it is too hot for paws. On a 25°C day, asphalt in direct sun can exceed 50°C — enough to blister pads within minutes.
Pads burn silently. Dogs keep walking because they are following you, and the damage shows up hours later as limping, redness, and peeling skin.
When to walk
- Early morning, before the sun has been on surfaces for long
- Late evening, after the ground has cooled — remembering that concrete and asphalt hold heat for hours after air temperature drops
- Not between 11am and 5pm in hot weather, for any dog
- Grass and shade rather than pavement and open ground
- Shorter, more often, rather than one long walk
On genuinely hot days, skip the walk. A dog will not suffer from one missed walk; a sniffing game indoors, a puzzle feeder and some training meets the need perfectly well. Heatstroke is not recoverable in the same way.
Which dogs are at highest risk
- Brachycephalic breeds — Bulldogs, French Bulldogs, Pugs, Boxers. Their airways are already compromised, and research has found substantially higher heatstroke risk. Some studies place the risk for flat-faced breeds at several times that of other dogs
- Overweight dogs. Fat insulates and increases the metabolic load
- Thick or double-coated breeds
- Very young and very old dogs
- Dogs with heart or respiratory disease
- Dogs with laryngeal paralysis, which specifically impairs the ability to move air
- Dark-coated dogs, which absorb more heat
- Unfit dogs, and dogs exercising harder than usual
- Any dog on a hot day who is chasing a ball. Exertional heatstroke is the most common form, and dogs will run themselves into it because the game overrides the signal
The signs
Early: heavy panting, drooling, bright red gums, restlessness, seeking shade, slowing down or lagging.
Progressing: thick sticky saliva, rapid heart rate, vomiting or diarrhoea, wobbliness, confusion, glazed eyes.
Severe: collapse, seizures, bleeding, unconsciousness. Gums may become pale or bluish.
Do not wait for the later signs. A dog who is lagging behind and panting hard on a hot walk is already in trouble.
What to do — the first five minutes
- Stop and get into shade immediately
- Pour cool water over the whole body, continuously. Current evidence supports aggressive early cooling, including immersion in cool water where available. The old advice to use only tepid water has been revised — cooling fast matters more than cooling gently
- Create airflow — a fan, an open car window while driving, anything moving air over wet fur
- Offer small amounts of cool water to drink if conscious
- Go to a vet immediately, cooling on the way
Do not cover the dog with wet towels and leave them — a towel that warms up traps heat.
Do not assume a dog who seems better is fine. Heatstroke causes internal organ damage, clotting problems and kidney injury that develop over the following hours and days. Every suspected case needs veterinary assessment.
Practical kit for summer walks
- Water and a collapsible bowl, always
- A cooling coat or a wet towel to drape (wetted repeatedly, not left to dry)
- A route with shade and water access
- Paw protection if you must walk on hot surfaces
Other summer hazards
Blue-green algae in ponds and lakes. Can kill within hours. If a lake looks green, scummy or has a warning sign, keep the dog out and do not let them drink.
Sea water. Causes vomiting and, in quantity, dangerous sodium levels. Take fresh water to the beach.
Sunburn. Pale-coated, thin-coated and hairless dogs burn, particularly on the nose, ear tips and belly. Use a dog-specific sunscreen; some human ingredients are toxic if licked.
Grass seeds, which peak in summer and migrate into paws, ears and eyes.
Adders and other wildlife, more active in warm weather.
Barbecues. Cooked bones, skewers, corn cobs, fatty meat, and hot coals.
Do not shave a double coat
The instinct is understandable and the effect is the opposite of what people expect. The undercoat insulates against heat as well as cold, and the guard hairs block direct sun.
Shaving removes the sun protection, frequently damages the coat permanently, and increases the risk of sunburn. Instead, remove dead undercoat with a rake, which improves airflow without removing the structure.
Single-coated breeds — Poodles, Bichons and similar — can be clipped shorter for summer without this problem.
And the car
Never, for any length of time, with any window arrangement, on any day above about 18°C. Interior temperatures rise dramatically within the first fifteen minutes.
If you see a dog in distress in a locked car, ring the police.
