Dog Heatstroke: Early Signs, First Aid and Prevention

Heatstroke is a medical emergency in which a dog’s body temperature rises beyond its ability to cool safely. It can happen during exercise, in parked vehicles, in poorly ventilated spaces or simply from being outside too long in hot and humid conditions.

Early warning signs

• very rapid or heavy panting;
• restlessness or distress;
• heavy drooling;
• bright-red or abnormal gums;
• slowing down or refusing to continue;
• vomiting;
• poor coordination.

The Merck Veterinary Manual lists rapid panting, drooling, vomiting, loss of coordination and collapse among heatstroke signs.

First action: stop the heat exposure

Move the dog into shade or air conditioning immediately. Begin cooling while arranging veterinary care. Heat injury can continue to affect organs even when the dog appears more alert.

Use cool water, not an ice bath

Wet the dog with cool water and improve airflow with a fan if available. Avoid plunging an overheated dog into very cold water. Aggressive cold-water immersion can complicate controlled cooling.

Seek veterinary care even after apparent improvement

Heatstroke can injure the gastrointestinal tract, kidneys, brain and clotting system. A dog that recovers enough to stand may still need examination, monitoring and treatment.

Dogs at greater risk

Short-nosed breeds, overweight dogs, seniors, dogs with heart or airway disease and dogs exercising intensely are more vulnerable. Thick coats and high humidity can also make cooling harder.

Prevention on walks

• exercise during cooler parts of the day;
• carry water;
• choose shaded routes;
• shorten activity when humidity is high;
• watch the dog, not the distance target;
• avoid hot pavement.

Never rely on a cracked car window

A parked vehicle can become dangerously hot quickly. If the dog cannot accompany you safely, leave the dog at home.

Build heat safety into outdoor plans

Our dog outdoor safety checklist covers water, wildlife and environmental hazards, while winter paw care handles the opposite seasonal extreme.

Hot pavement can be a separate injury

A dog may avoid hot ground before showing whole-body heatstroke. Test walking conditions conservatively and choose grass or shade when pavement is uncomfortable. Paw burns and systemic overheating can happen together but require separate evaluation.

Cooling during transport

Continue gentle evaporative cooling while traveling to veterinary care if the dog remains hot and your veterinary team advises it. Air conditioning and airflow can help. Do not wrap the dog in wet towels for a long trip because trapped material can reduce evaporation as it warms.

Why humidity changes the risk

Dogs rely heavily on panting for evaporative cooling. High humidity makes evaporation less efficient, so a temperature that feels manageable on a dry day can become much harder during humid weather.

Build a personal heat threshold

Do not use one universal temperature cutoff for every dog. Track how your dog handles short walks at different heat and humidity levels, taking breed, age, weight, fitness and medical history into account. When recovery from normal activity takes longer than usual, reduce intensity rather than trying to condition through the heat.

After a heat injury

Follow veterinary recheck instructions even if the dog seems normal at home. Some complications are delayed, which is why a serious overheating event should not be treated as “fixed” simply because panting has slowed.