A dog can only cool down by panting and through the pads of its paws. That makes a mild-feeling day riskier than it looks, especially on a walk, when your dog is working hard in the sun. Dogs Trust sums it up as "Twenty is Plenty": once it reaches around 20°C, keep exercise short, around 20 minutes, and walk when it is cooler.
The quiz below turns that idea into a quick check. Put in the temperature, tick what applies to your dog, and see how to plan the outing. It is a rule of thumb, not a vet's verdict.
Dogs Trust names flat-faced breeds, older dogs, overweight dogs and dogs with health conditions as higher risk, and the RSPCA adds puppies, thick-coated dogs and dogs with breathing problems. That is why the quiz adds a step for each one. Heatstroke can still hit any dog, so no breed is fully safe.
Walking time matters too. Early morning and late evening are cooler, but tarmac holds heat long after sunset, so keep running the hand test.
Press the back of your hand on the pavement for seven seconds. If it is too uncomfortable for you, it is too hot for your dog's paw pads. The Kennel Club says to pick grass over hard surfaces and avoid the midday sun. Limping, licking the paws, or red, swollen or blistered pads can mean a burn: get off the surface, rinse the paws with cool water and call your vet.
If it is too hot for the back of your hand, it is too hot for your dog's paws.
Heavy or noisy panting, thick drooling, vomiting, wobbliness, weakness or collapse can all be signs of heatstroke, and it is an emergency. Stop exercising straight away, move your dog into shade, and pour cool water over the neck, tummy and thighs, avoiding the head. Fan them if you can. Call a vet right away and travel in a cool, ventilated car. Never leave a dog in a parked car, even for a minute.
This guide is general care advice, not veterinary advice. If you are worried about your dog, ask a vet.