Dog Heatstroke: Signs, Risks, and How to Prevent It

Dogs cool themselves mainly by panting. They sweat only through their paws, so they cannot shed heat the way people do¹. When the air is hot or humid, or when a dog exercises hard, panting may not be enough, and body temperature can climb into the danger zone.

Cornell University's veterinary college describes heatstroke as occurring at a body temperature of 105°F or higher¹. The LSU School of Veterinary Medicine also describes 105°F as the point where heat-related illness can occur⁴. The two sources give slightly different normal ranges, so a number alone should not replace a veterinarian's judgment. Never rely on a home thermometer reading to decide whether to seek care. If you suspect heatstroke, treat it as an emergency.

Signs reported by veterinary sources include:

• Heavy panting and drooling¹
• Hot skin, rapid panting, and visible distress²
• Vomiting and diarrhea, which may contain blood¹
• Gums that change from light pink to bright red or dull gray-pink⁴
• Weakness, confusion, uncoordinated movement, and seizures¹²
• Collapse or loss of consciousness²

Cornell notes that prolonged high temperature can damage many organs, and commonly causes acute kidney injury, clotting problems, and shock¹. LSU says untreated cases can progress to organ failure, coma, and death⁴. A dog that looks better after cooling off can still have internal damage, so a veterinary exam is still needed.

Any dog can overheat, but veterinary sources name these groups as more vulnerable:

• Short-nosed (brachycephalic) breeds such as Pugs and Bulldogs¹⁴. The Merck Veterinary Manual notes that short-nosed breeds can overheat from stress or excitement even on cool days².
• Overweight dogs, older dogs, and puppies¹³⁴.
• Dogs with thick or dark coats¹³.
• Dogs with breathing or heart conditions, such as laryngeal paralysis or heart disease¹.

Cornell also lists hot or humid environments, strenuous exercise, and lack of shade or water as common causes¹. The sources I read do not give a specific humidity number at which risk jumps, so there is no safe “cutoff” to memorize. If it feels muggy to you, your dog is likely feeling it too.

A parked car can heat up very quickly. The Merck Veterinary Manual says cracking a window or parking in the shade does not reliably keep pets safe, and that a car can reach dangerous temperatures within minutes³. LSU gives the same warning: even a few minutes, or shade, or windows partly down, can be life-threatening⁴. Cornell lists never leaving a dog unattended in a car as a key prevention step¹.

The practical rule is simple. If the dog cannot come inside with you, leave the dog at home, even for a quick errand.

• Pick cooler times. LSU advises early morning or late evening for walks and avoiding midday jogging or biking in summer⁴. Cornell suggests avoiding the hottest part of the day and staying indoors in extreme heat and humidity¹.
• Match exercise to the dog. LSU suggests adjusting activity to age, breed, and body condition and asking your veterinarian for guidance⁴.
• Provide shade and water. Offer frequent access to fresh water and shade when your dog is outdoors¹⁴.
• Check the ground. The Merck Veterinary Manual says hot asphalt and sand can cause serious burns on paws³, and LSU says hot pavement can burn paw pads⁴. The sources I read do not give a simple surface temperature rule. A common approach is to touch the surface with your own hand, and if it is too hot for you to hold comfortably, choose grass or another route. That check is practical advice, not a figure from these sources.

Heatstroke is a medical emergency. First aid is meant to start cooling while you get help, not to replace it. At a high level, the Merck Veterinary Manual and Cornell describe these steps¹²:

1. Move the dog out of the heat and into shade or air conditioning.
2. Start cooling right away with cool water, such as by wetting the coat. Merck also mentions wet towels and a fan, with a focus on the belly².
3. Take the dog to a veterinarian immediately. Cornell suggests running the car's air conditioning with the dog in front of a vent on the way¹. Calling the clinic on the way lets them prepare.

Merck warns not to immerse the animal in cold water². Sources differ somewhat on details, such as whether ice packs are appropriate, so follow the instructions of the clinic if you reach them by phone.

Veterinary treatment can include active cooling, IV fluids, oxygen, and monitoring for organ damage¹. LSU notes that all heatstroke cases need prompt treatment and monitoring for several days⁴. Cornell says many dogs with heatstroke do not survive, that survival depends on how high the temperature gets and for how long, and that dogs that survive are at greater risk of heatstroke again¹.

The sources agree on the main points but differ on small details, including the normal body temperature range. They do not give a humidity or pavement temperature threshold, and this article does not either. Individual risk depends on the dog's health, coat, fitness, and the conditions, so ask your veterinarian what is reasonable for your dog.