Most dogs love going for walks, romping at the dog park, leaping for Frisbees or sprinting for tennis balls. But during the “dog days of summer,” when temperatures are soaring, letting dogs overexert themselves (or forcing them to) isn’t doing them any favors. In fact, it could do them in.

Dogs simply can’t handle the heat. Unlike humans, they can only cool themselves by panting and sweating through their footpads. When ambient temperatures rise above 89.5 degrees, they can’t effectively shed their body heat, and when their body temperature reaches 106 to 109 degrees, heatstroke sets in, resulting in brain damage or death. Those who are elderly, overweight or flat-faced—such as pugs, boxers, bulldogs and other breeds—are especially at risk.

Making dogs run with you while you jog or bike during hot weather can kill them—they will collapse before giving up, and by then it may be too late to save them. Even those who are used to running and in good physical shape are in danger: Last month, for example, Mojo, a K9 officer with the Arlington Police Department in Texas, reportedly became overheated while pursuing a fugitive. Despite being rushed to an animal hospital, he didn’t survive.

Hot pavement, sand and other surfaces can scorch dogs’ sensitive footpads, causing pain, burns and permanent damage, as well as reflecting heat back onto their bodies. In Arizona last month, a pit bull reportedly died of heat exhaustion while hiking on a trail in 107-degree temperatures. The dog’s guardian called the police for help, but by the time the first responders arrived, it was too late.

You can protect your dog by walking early in the morning and late at night when it’s cooler and always testing the ground with your hand—hot to the touch is too hot for Spot. Choose shady routes, and walk on the grass instead of the pavement. Carry plenty of water and stop often in the shade to rest and take a water break.

Exercise and sweltering temperatures are a deadly combination for dogs, but the ones who can’t move are just as vulnerable on summer days. Countless dogs have suffered and died of heatstroke because they were chained or penned outside with no escape from the blazing sun and blistering heat.

In July, both a puppy and an adult dog in North Carolina reportedly died after their tethers became tangled in a bush, trapping them in direct sunlight with no access to shade or water. Also last month, a Labrador retriever in Maryland reportedly died after being left on a second-story deck in 90-degree weather. According to the police, the deck’s surface was even hotter—109 degrees.

Never leave dogs outdoors unattended, especially in the heat, and if there are chained or penned dogs in your neighborhood, check on them often to ensure that they have water (in a tip-proof container) and shade (as well as food and shelter), and encourage your neighbors to let them live indoors. If they lack these basic necessities, provide them with water and notify local authorities immediately.

It should go without saying, but hot cars are also death traps for dogs. Never leave an animal (or child) in a parked car in warm weather, even for a short period of time with the windows slightly open. Dogs can succumb to heatstroke within minutes—even if the car isn’t parked in direct sunlight. If you see a dog in a hot car, ask nearby businesses to page the vehicle’s owner or call 911 immediately. If the dog appears to be in imminent danger (e.g., rapid panting, bright red tongue, dizziness, vomiting), quickly find a witness who can confirm your account if possible and then take whatever action is necessary to save the animal’s life.

During the “dog days of summer”—and always—keep your dogs safe by keeping them indoors, with air conditioning or fans running and plenty of fresh, cool water available. Special cooling mats and vests for dogs can also help keep them comfortable.

And please, spread the word: Heat kills.