You set up the kiddie pool, bought the cooling mat, and added ice cubes to the water bowl. Your dog walked past all of it and went to lie directly in the sun. This is a tale as old as pet ownership, and there’s a legit reason for it.
TrustedHousesitters, the global pet-sitting platform, spoke with Dr. Stevie Aitken, a U.S.-based emergency and small animal veterinarian, about why dogs seek out sunny spots even during a heatwave. The answer comes down to instinct. Dogs run at a higher body temperature than humans, and warmth feels good to them—it helps them relax, eases mild muscle stiffness, and, for older dogs, can bring physical relief. Sunlight also triggers serotonin release, giving dogs something close to the mood boost humans get from a sunny day. They don’t care that it’s 90 degrees outside.
The problem, Dr. Aitken explains, is that instinct doesn’t come with a built-in warning system. “Dogs and cats don’t recognize the dangers of overheating in the way people do,” she told TrustedHousesitters. “Once they’re settled or asleep in the sun, they may not move until they’re already overheating.” Dogs cool themselves primarily through panting, which is efficient up to a point—but once a dog is deeply relaxed in a sun patch and the temperature keeps climbing, they can slip into heat stress before they’ve even realized there’s a problem.
Not every dog handles heat the same way. A 2025 review in Frontiers in Animal Science found that brachycephalic breeds (short snouts and flatter faces)—French Bulldogs, Pugs, Bulldogs—are at particular risk because their shortened airways make panting a much less effective cooling tool than it is for other dogs. Older dogs, puppies, overweight animals, and those with heart or breathing conditions also sit in a higher-risk group. Dr. Aitken’s advice for these dogs during a heatwave is simple: keep them inside, and take them out only when they need to go to the bathroom.
How to Tell Your Dog Has Been in the Sun Too Long
Healthy dogs without those risk factors can still enjoy a sun patch—they just need someone watching them while they do it. Dr. Aitken’s guidance is to keep shade and fresh water accessible at all times rather than cutting sun time out completely. One thing owners of pale or thin-coated dogs often miss: those dogs can burn, especially on the ears and nose. A vet can recommend a pet-safe sunscreen for exposed areas.
If a dog shows excessive panting, heavy drooling, weakness, vomiting, or collapse, Dr. Aitken says to move them to shade immediately and apply cool (not ice-cold) water. Ice-cold water can cause blood vessels to constrict and actually slow the cooling process. Then call a vet. “Acting quickly can make all the difference,” she said.
The sun isn’t the enemy. It’s just that dogs can’t tell the difference between what feels good and what’s dangerous. That’s your job.
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