What Every Dog Parent Needs to Know About Hot Weather

Analysis by Dr. Karen Shaw Becker

hot weather dog breeds

Story at-a-glance -

  • With heat waves on the rise, researchers at England’s Nottingham Trent University explored risks factors in dogs that increase the incidence of heat-related illness (HRI), or heatstroke
  • Nine breeds had a higher risk of heatstroke, including the chow chow, bulldog, French bulldog, dogue de Bordeaux, greyhound, cavalier King Charles spaniel, pug, English springer spaniel and golden retriever
  • Five of the nine breeds with increased HRI risk were brachycephalic, or flat-faced, breeds
  • Dogs that were overweight or weigh over 50 kilograms (110 pounds) had a higher risk of heatstroke in the study, as did dogs over the age of 2, although dogs 12 years or older had the greatest risk
  • Purebred dogs were also more likely to have heatstroke than crossbred dogs, or mutts, likely because they’re more likely to have exaggerated features, including thicker coats and extreme body size and skull shapes

Any dog can suffer from heat-related illness (HRI), which can cause heart trouble, problems with normal heat-dissipation mechanisms, organ failure and death. However, certain breeds are more susceptible than others. With heat waves on the rise, researchers at England’s Nottingham Trent University explored risks factors in dogs that increase the incidence of HRI, or heatstroke.1

Heatstroke in dogs is caused by a dangerously high body temperature. It sometimes makes headlines due to tragedies that occur when dogs are left in hot vehicles, but dogs can overheat in a variety of other situations as well, including during outdoor exercise and due to lack of hydration and obesity. The featured study also revealed a number of risk factors that may increase dogs’ risk, starting with their breed.

Breeds Most at Risk of Heatstroke

The researchers evaluated clinical records for 905,543 dogs, finding heat-related illness events in 395 cases. Breeds with the highest incidence of heatstroke included:2

Chow chow

Bulldog

French bulldog

Dogue de Bordeaux

Greyhound

Cavalier King Charles spaniel

When compared to Labrador retrievers, which served as the control group, nine breeds had a higher risk of heatstroke, including the six above along with pugs, English springer spaniels and golden retrievers.

Flat-faced (brachycephalic) dogs are well known to struggle with breathing issues and have trouble keeping their body temperatures in the normal range. Not surprisingly, the study also found that dogs with a brachycephalic skull shape are at greater risk of heat-related illness — five of the nine breeds with increased HRI risk were brachycephalic.

As I’ve been saying for some time, the breeding of dogs with conditions like brachycephaly that seriously compromise their health, longevity and quality of life should be discouraged, and the researchers agreed, noting, “Breeding for good respiratory function and maintaining a healthy bodyweight should be considered key welfare priorities for all dogs to limit the risk of heat-related illness.”3

Dogs that were overweight or weigh over 50 kilograms (110 pounds) had a higher risk of heatstroke in the study, as did dogs over the age of 2, although dogs 12 years or older had the greatest risk.4

In humans, the elderly are more prone to heatstroke due to changes in sweat production and decreased skin blood flow, which reduces the body’s ability to dissipate heat. It’s possible that similar age-related changes also occur in dogs. Body size also made a difference, with smaller dogs at a slight advantage:5

“Smaller dogs have a high heat storage to radiative surface area ratio that results in more rapid heat loss compared to larger dogs, meaning they can exercise for longer before overheating. This increased efficiency in radiative heat loss could explain why the purebred breeds with the lowest odds of HRI are all small breed dogs.”

Three Breeds With the Lowest Heatstroke Risk

Ironically, the dogs with the lowest odds of heatstroke — Lhaso Apso, Shih tzu and Chihuhua — were all brachycephalic breeds, but they were small in size, typically weighing under 10 kilograms (22 pounds).

There were some surprises in the study as well, like the finding that the golden retriever has a 2.67 times higher risk of heat-related illness compared to the Labrador, which the researchers suggested may be due to its thicker coat.

Purebred dogs were also more likely to have heatstroke than crossbred dogs, or mutts, likely because they’re more likely to have exaggerated features, including thicker coats and extreme body size and skull shapes.

As might be expected, wild dogs would be expected to fare better in the heat than their domestic counterparts. According to the study:6

“In comparison, wild dogs such as the African Hunting dog, have been shown to tolerate higher core body temperatures than domestic dogs during exercise in hot climates (41 °C), and lose a greater proportion of the heat generated through non-evaporative mechanisms effectively conserving water.”

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The Most Common Cause of Heatstroke in Dogs

No matter your dog’s age, size or breed, it’s important to know the signs and symptoms of heatstroke, as well as what may cause it. Unbeknownst to many, the most common cause of heatstroke in dogs is exercise with their owners, with warm weather exertion or exercise, which could include walking, playing or running, being responsible for 74% of heatstroke cases in one study.7

It’s important to watch your pet carefully when it’s warm outside, especially if you’re engaging in physical activity. Symptoms of overheating include the following:

Elevated body temperature

Weakness, collapse

Heavy panting or rapid breathing

Bright or dark red tongue, gums

Excessive drooling

Staggering, stumbling

Glazed eyes

Vomiting, bloody diarrhea

Excessive thirst

Seizures

Increased pulse and heartbeat

Unconsciousness

If you notice any of these signs, take immediate action. If symptoms are severe, get to an emergency veterinary hospital right away, but if he’s able to stand, you can offer small sips of water and check his temperature rectally. If his temperature is 104°F or lower, you can call your veterinarian for instructions on what to do next.

However, for higher temperatures, you need emergency medical care. On the way, you can start cooling down his body by soaking his body with cool (not cold) water, using a hose, wet towels or any other available source of cool water, concentrating on his head, neck and the areas underneath the front and back legs. Be sure to seek veterinary care, even if it seems like your dog is recovering.