Not long ago, the Miami evening news ran the story of a chihuahua named Fiji, who was seen locked in a hot car while her owner dined with her family at the mall. By the time a police officer busted open a car window to get the dog to safety, the small pooch was unconscious. Rushed to the Sky Lane Animal Hospital in Miami, Fiji was treated for heat stroke and released — to a new owner.

Sadly, not every story about dogs and hot cars has a happy ending. Hundreds of dogs die in hot cars every year, vets say, when their owners leave them and dash into a store “for just a couple minutes.” Few owners realize how quickly a car can turn into a deadly sauna. In many cars the temperature can heat up 20 degrees every 10 minutes, even in the shade with the windows cracked open.

Dogs can suffer brain damage and die when their core body temperature reaches 107 degrees F. Unlike us, they cannot sweat to lower their body temperature; they get rid of heat by panting and, to a much lesser extent, through the pads of their feet, says Cam Hornsby, DVM, medical director for three Middle Tennessee pet emergency clinics. There’s a really short window, he says, between a dog seeming OK and becoming dangerously overheated.

On a hot day, in fact, a dog in a locked car can die within minutes. If it’s 85 degrees outside, the inside of the car will climb to a hazardous 104 degrees in 10 minutes. In another 10 minutes, the temperature inside the car will soar to 114 degrees, according to the American Veterinary Medicine Association. If it’s 95 degrees outside, the car could reach 114 degrees in only 10 minutes. In an hour, it would be 140 degrees.

Leaving your dog inside the car on a cooler day is also dangerous. On a balmy 70-degree day, the temperature inside the car could climb to 104 degrees in 30 minutes. In just over an hour, the inside of the car would be 115 degrees.

What about a little errand?

It’s just not worth it. That’s the mantra from animal experts when asked if it’s ever OK to leave your dog inside a parked car, even for a minute.

“There’s not any time I’m going to feel completely comfortable” leaving a dog in a car, says Joe Ed Conn, DVM, a veterinarian in Nashville. Even on a relatively cool day, he says, “the car is going to heat up.”

You also never know how long that tiny little errand will take, cautions KC Theisen, DVM, director of pet care issues with the Humane Society of the United States. “You’re running into the supermarket for one thing, but when you get to the checkout line five people are in front of you. You can’t control that.”

Nor can you predict when a random accident might occur. In a recent newspaper account, a pet owner tripped and was knocked unconscious while dashing into a bank on a quick errand. By the time he came to and got someone to check on his pet, the dog was dead.

Related: The Safe Way to Travel with Your Dog in the Car

Vets SafeBee interviewed say they see fewer overheated dogs these days. That’s partly because more people are more aware of the dangers and don’t leave their dog unattended. But tragically, it’s also because the heat is often so intense that by the time the owner returns to the car, the dog has already died. “Most of the time it’s because they forgot the dog was in the car. It’s always so sad,” says Adesola Odunayo, DVM, who teaches emergency and critical care at the University of Tennessee Veterinary Medical Center.

How long it takes for heat inside a car to kill a pet depends on a mix of things, including the temperature and humidity and the dog’s breed, anxiety level and general physical condition. Flat-faced, snub-nosed dogs (brachycephalic dog breeds in vet speak), such as bulldogs, boxers and pugs, have particular difficulty with heat, vets say.

Locked in a hot car, a dog will pant in an effort to get cooler, whine, bark and scratch at the window in distress. As the temperature rises, he may vomit, develop diarrhea, or bloody himself trying frantically to dig out of the car. His condition may march inexorably from heat stress to heat exhaustion and finally to heat stroke, which can include seizures and neurological problems, Conn says. Finally, the heart and other organs will shut down.

“I can only imagine how helpless and frightened the dog must be”

With more than 20 years as a veterinarian in general practice, Ernie Ward, DVM, of North Carolina was so disturbed about dogs in hot cars that he locked himself in a car on a typical summer day for 30 minutes to publicize the issue. All four windows were cracked open an inch or two and there was a steady breeze outside, but in 30 minutes the temperature inside the car had climbed from 94 degrees to 116 degrees.

“It’s stifling in here, oppressive… It’s almost unbearable,” a visibly distressed Ward tells viewers in the video, which was posted on YouTube.

“Everything in me is saying, get out, get out! This is getting dangerous…I can only imagine how helpless and frightened a dog must feel.”

Ward, sweating profusely toward the end of the video, reminds viewers that dogs cannot sweat to relive the heat. He told SafeBee he wanted to share “how quickly things can escalate to a dangerous if not deadly temperature.” Along with other experts, he urges pet owners to “never, ever leave your dog in a parked car.”

Related: Doggie First Aid Kit

When to see the vet

If you ever do have to rescue your pet or another dog from a hot car, how do you know if he has heat exhaustion or heat stroke?

Watch for rapid breathing and darkening of the dog’s mucus membranes from the usual pink to bright red, Conn says. Other signs include vomiting and bloody diarrhea, and the dog may collapse. Conversely, the pet may seem drunk or lethargic, Hornsby says. “You don’t want to ignore that, thinking they’re just tired. Either call your vet or take them to an emergency clinic.”

Related: Signs of Heatstroke in a Dog and How to Avoid It

Race the dog to the vet right away if you suspect heat problems, says Odunayo. Owners can (and should) cool down their pets with warm or tepid water before going to the vet, if at all possible. (Avoid cold or ice water.) After dousing their pooch, some people think the animal will be fine until they get to the vet a few days later. That’s not usually a good idea, she says. It’s better to seek help as fast as possible. 

“When a dog comes in in heat stroke, we don’t paint a pretty prognosis,” Hornsby says. People think that as soon as we cool them off the dog will be OK, he says, but that’s not the case. Vets will cool the dog, provide other treatment such as transfusions then keep the dog for a few days for observation.

“We’ll usually know within two to three days if the dog will have lasting damage from overheating,” he says. “We worry a lot about the kidneys, but a dog can also suffer serious central nervous system problems because of overheating."

Related: When to take your dog to the vet

What to do if you see a dog locked in a hot car

What should you do if you see someone else’s dog struggling inside a hot car? Theisen of the Humane Society offers these tips:

  • Write down a description of the car and the license plate number, go to nearby businesses and ask the manager to make a courtesy announcement asking the owner to return to the car and check on their pet. Most owners will respond right away.
  • If you believe the animal is in distress, call law enforcement to come and take action.Mall security may be able to help as well. In the meantime, it’s safest for everyone to try to find the owner.

The best approach, vets agree, is awareness and prevention. Ironically, some people whose dogs are injured or killed in a hot car may be among the owners who are most attached to their pets. “I usually honestly tell people not to take their dog with them when they go out,” Hornsby says. “Some clients like to take their dogs everywhere, especially if the dog has separation anxiety.…It’s just not worth it in the summer. It’s better to keep them indoors.”

Kathleen Carlson is a Nashville freelance journalist. She has written for The Tennessean, Nashville Banner, Nashville Ledger and other publications, covering business, crime and courts, workplace issues, general assignment and features. In addition, she has written specialty publications for human resources managers, copy edited at two daily newspapers and edited a small newspaper for a Middle Tennessee religious community. Her favorite safety suggestion is to use sunscreen every day.