Most pet owners know that leaving a dog or cat in a parked vehicle is dangerous. What many people don’t realize is how quickly a seemingly comfortable pet can become a critically ill emergency patient.
Every summer, veterinary emergency hospitals treat dogs and cats suffering from heat-related illness after being left in vehicles. In some cases, the outcome is fatal. In others, pets survive but experience serious complications affecting multiple organ systems.
At Boundary Bay Veterinary Specialty Hospital in Surrey, our Emergency and Critical Care team manages severe heat-related emergencies every year. Understanding what happens inside the body during heatstroke can help owners appreciate why even a few minutes in a parked vehicle can become life-threatening.
Why a Parked Vehicle Can Become Deadly in Minutes
One of the most common misconceptions is that a parked vehicle is safe if the outside temperature feels mild or if the windows are left partially open.
In reality, the interior of a parked vehicle can heat rapidly, creating temperatures that quickly become dangerous for pets. Cars act like greenhouses, trapping heat and limiting air circulation.
Unlike humans, dogs and cats cannot efficiently cool themselves through sweating. Dogs rely primarily on panting, while cats depend on grooming, behavioural changes, and limited sweating through their paw pads. As temperatures rise, these cooling mechanisms can quickly become overwhelmed.
Many heatstroke cases occur when owners believe they will only be away briefly. Unfortunately, heat-related illness does not follow a predictable timeline. Factors such as humidity, vehicle colour, sun exposure, ventilation, and the individual pet’s health can all influence how quickly temperatures become dangerous.
Cracking windows provides little protection, and relying on a vehicle’s air conditioning system is risky if the system shuts off unexpectedly or malfunctions.
The safest rule is simple: If your pet cannot accompany you inside, leave them safely at home.
What Happens During Heatstroke?
Heatstroke is much more than simply becoming overheated.
Veterinarians consider heatstroke a medical emergency because elevated body temperature can affect nearly every organ system in the body.
As body temperature rises, proteins and cellular structures throughout the body begin to malfunction. This can trigger widespread inflammation and injury affecting multiple organ systems. Circulation may become compromised, normal cellular processes can begin to fail, and damage may continue even after a pet has been removed from the hot environment.
Patients may experience:
- Gastrointestinal injury and damage to the intestinal barrier
- Abnormal blood clotting and bleeding disorders
- Kidney injury
- Cardiovascular instability
- Neurologic dysfunction, including seizures or altered consciousness
- Respiratory compromise
- Shock and multiple-organ dysfunction
The longer elevated body temperatures persist, the greater the risk of serious complications.
Heatstroke is considered a true multisystem emergency. One of the challenges facing our Emergency and Critical Care specialists is that some of the most serious complications may not become fully apparent until hours after the initial overheating event.
Why Some Pets Are at Greater Risk
Any dog or cat can develop heatstroke under the wrong conditions.
However, some pets may be at increased risk, including:
- Brachycephalic (short-nosed) breeds
- Senior pets
- Very young animals
- Overweight pets
- Pets with heart disease
- Pets with respiratory disease
- Pets with underlying medical conditions
These patients may have a reduced ability to regulate body temperature and can become critically ill more quickly.
Warning Signs of Heatstroke
One of the challenges with heatstroke is that clinical signs can progress rapidly.
Owners may observe:
- Excessive panting
- Thick saliva or drooling
- Restlessness
- Weakness
- Vomiting
- Diarrhea
- Bright red gums
- Disorientation
- Collapse
- Seizures
Cats may show more subtle signs initially, which can make early recognition more difficult.
Any pet displaying signs of overheating should be treated as a medical emergency.
Why Heatstroke Can Continue to Worsen After Cooling Down
One of the most concerning aspects of heatstroke is that improvement on the surface does not always mean the danger has passed.
A pet may appear more comfortable after being removed from a hot environment and cooled appropriately, while internal injury continues to develop.
At Boundary Bay Veterinary Specialty Hospital, our Emergency and Critical Care specialists often monitor heatstroke patients for complications involving:
- Kidney function
- Blood clotting abnormalities
- Gastrointestinal injury
- Cardiovascular stability
- Neurologic function
Because some complications develop gradually, veterinary evaluation is recommended even when a pet appears to recover after a heat-related event.
What Should You Do If You See a Pet in a Hot Vehicle?
If you encounter a pet inside a parked vehicle and are concerned about its welfare:
- Note the vehicle’s make, model, colour, and licence plate.
- Ask nearby businesses to page the owner.
- Monitor the animal from a safe location.
- Contact local animal control, police, RCMP, or the BC SPCA Animal Helpline if the pet appears distressed.
- Do not break the vehicle’s window yourself.
In British Columbia, the legal authority to enter a vehicle and remove an animal rests with designated enforcement personnel, including police officers, RCMP members, animal control officers, and BC SPCA Special Constables. Attempting to enter a vehicle yourself may place you, the animal, and others at risk.
First Aid for Suspected Heatstroke
If a pet has been removed from a hot environment and is showing signs of heat-related illness:
- Move the animal to a cool, shaded area.
- Begin cooling with cool or lukewarm water.
- Avoid ice baths or ice packs.
- Use fans to assist with evaporative cooling.
- Offer small amounts of water if the pet is alert and able to drink.
- Seek immediate veterinary care.
Even if a pet appears to improve, internal complications may continue to develop after body temperature begins to normalize.
How Emergency and Critical Care Specialists Treat Heatstroke
For emergency veterinarians, lowering body temperature is only one component of treatment. Because heatstroke can affect multiple organ systems simultaneously, patients often require comprehensive diagnostic evaluation, ongoing monitoring, and intensive supportive care.
Boundary Bay Veterinary Specialty Hospital, our Emergency doctors and Critical Care specialists may utilize:
- Continuous temperature monitoring
- Advanced bloodwork to assess organ function
- Blood pressure monitoring
- Coagulation testing to evaluate clotting abnormalities
- Oxygen therapy
- Intravenous fluid therapy
- Electrolyte monitoring and correction
- Diagnostic imaging when complications are suspected
- Intensive nursing care and ICU-level monitoring
Our Emergency and Critical Care team frequently collaborates with our Internal Medicine, Diagnostic Imaging, Surgery, and other specialty services when managing severe heatstroke cases. Depending on the patient’s condition, additional diagnostics may be recommended to evaluate organ function, monitor for complications, and guide treatment decisions.
Because heatstroke can affect several body systems at once, clinicians are often monitoring multiple organ systems simultaneously while treatment is underway.
Why Heatstroke Remains a True Emergency
One of the most dangerous misconceptions about heatstroke is that if a pet cools down, the emergency is over. Unfortunately, heatstroke can continue causing injury long after the initial overheating event.
Complications affecting the kidneys, gastrointestinal tract, clotting system, nervous system, and cardiovascular system may develop hours after exposure. For this reason, pets that have experienced significant heat exposure should be evaluated by a veterinarian even if they seem to improve.
Protecting Pets This Summer
The good news is that heatstroke caused by parked vehicles is almost entirely preventable.
Before running errands, ask yourself one simple question: Can my pet safely come inside with me?
If the answer is no, the safest choice is to leave them at home in a cool, comfortable environment.
Heatstroke is one of the few veterinary emergencies that is almost entirely preventable, yet it remains a cause of avoidable illness and death in pets every summer.
At Boundary Bay Veterinary Specialty Hospital in Surrey, our VECCS Level I-certified Emergency and Critical Care Service is equipped to manage life-threatening emergencies, including severe heatstroke and its complications. Our Emergency and Critical Care specialists work closely with our Internal Medicine, Diagnostic Imaging, Surgery, and other specialty services to provide advanced care for critically ill patients.
When it comes to hot vehicles, prevention will always be safer than treatment—and a few minutes of planning can help prevent a life-threatening emergency.
Frequently Asked Questions About Pets in Hot Cars and Heatstroke
How dangerous is it to leave a dog in a parked car?
Leaving a dog in a parked vehicle can be extremely dangerous, even for a short period of time. Temperatures inside a vehicle can rise rapidly, creating conditions that may lead to heatstroke, organ damage, and potentially death.
Can a dog die in a hot car?
Yes. Heatstroke caused by being trapped in a hot vehicle can quickly become life-threatening. Severe cases may lead to shock, organ failure, seizures, and death.
Can cats get heatstroke in a parked car?
Yes. Although cats are less commonly seen riding in vehicles than dogs, they can develop heatstroke if left in a hot car. Cats may also show more subtle signs of heat-related illness, making early recognition especially important.
Why do cars become so hot for pets?
Parked vehicles act like greenhouses, trapping heat and limiting air circulation. Even when outdoor temperatures feel comfortable, the temperature inside a vehicle can rise rapidly and become dangerous for pets.
Does cracking the windows make a car safe for a pet?
No. Partially open windows provide little protection against rising temperatures inside a parked vehicle. Cracked windows should never be relied upon to prevent heatstroke.
Is it safe to leave the air conditioning running for my pet?
Relying on a vehicle’s air conditioning system can be risky. If the system shuts off, malfunctions, or the vehicle stops running, temperatures can increase quickly and place your pet at risk.
How do dogs and cats cool themselves?
Dogs primarily regulate body temperature through panting, while cats rely on grooming, behavioural changes, and limited sweating through their paw pads. Neither species cools themselves as efficiently as humans.
What happens inside the body during heatstroke?
Heatstroke can affect multiple organ systems. Elevated body temperatures may lead to widespread inflammation, gastrointestinal injury, clotting abnormalities, kidney injury, cardiovascular instability, neurologic dysfunction, respiratory compromise, shock, and multiple-organ dysfunction.
Why is heatstroke considered a medical emergency?
Heatstroke is a multisystem disease that can continue causing injury even after a pet has been removed from the hot environment. Serious complications may develop hours after the initial overheating event.
Which pets are most at risk for heatstroke?
Any dog or cat can develop heatstroke, but increased risk may be seen in brachycephalic breeds, senior pets, young animals, overweight pets, and those with heart disease, respiratory disease, or other underlying medical conditions.
What are the warning signs of heatstroke in dogs?
Signs may include excessive panting, drooling, weakness, vomiting, diarrhea, bright red gums, restlessness, disorientation, collapse, or seizures.
What are the signs of heatstroke in cats?
Cats may show panting, weakness, lethargy, drooling, vomiting, collapse, or behavioural changes. Their signs can sometimes be more subtle than those seen in dogs.
What should I do if I see a pet trapped in a hot car?
Note the vehicle information, ask nearby businesses to page the owner, monitor the animal, and contact local authorities, animal control, police, RCMP, or the BC SPCA Animal Helpline if the pet appears distressed.
Should I break a car window to rescue a pet?
No. In British Columbia, the legal authority to enter a vehicle and remove an animal rests with designated enforcement personnel such as police officers, RCMP members, animal control officers, and BC SPCA Special Constables.
What should I do if my pet is showing signs of heatstroke?
Move your pet to a cool, shaded area, begin cooling with cool or lukewarm water, use fans to assist cooling, offer small amounts of water if appropriate, and seek veterinary care immediately.
Should I use ice or an ice bath to cool an overheated pet?
No. Ice baths and ice packs are generally not recommended because they can interfere with effective cooling.
Can a pet seem better and still have heatstroke complications?
Yes. Heatstroke can continue causing injury after a pet’s body temperature begins to normalize. Veterinary evaluation is recommended even if a pet appears to improve.
How do Emergency and Critical Care specialists treat heatstroke?
Treatment may include temperature monitoring, advanced bloodwork, blood pressure monitoring, coagulation testing, oxygen therapy, intravenous fluids, electrolyte correction, diagnostic imaging, intensive nursing care, and hospitalization.
Why might a pet need hospitalization after heatstroke?
Some complications of heatstroke can develop hours after the initial event. Hospitalization allows veterinarians to monitor for organ dysfunction, clotting abnormalities, and other potentially life-threatening complications.
Is heatstroke caused by hot cars preventable?
Yes. Heatstroke resulting from being left in a parked vehicle is one of the most preventable veterinary emergencies. If your pet cannot safely accompany you inside, the safest option is to leave them at home.
