Never leave a pet in a parked car, even briefly, in the shade, or with the windows cracked. AVMA’s figures put the interior about 43°F hotter after an hour, and AVMA says cracking the windows makes no difference. Prevention beyond that comes down to shifting outings out of peak heat, planning around higher-risk pets, and using cooling gear for what it can actually do.
If you see a pet showing distress signs inside a parked car right now (heavy panting, drooling, collapse, or unresponsiveness), this is an emergency. If the car is yours or the owner is there to open it, get the animal out of the heat and begin cooling per our heatstroke response guide immediately. If it is a stranger’s locked car, make the call first: dial 911 or your local animal control before you touch the vehicle and say on the call that the animal is in distress. Of the six hot-car statutes covered in our guide to breaking a car window to save a dog, by state, five reach a private person at all, and every one of those five conditions its protection on that contact. Make the call fast, not last.
Our dog heatstroke response guide owns recognition, signs, and cooling steps, sourced from the AVMA, Cornell, the American Red Cross, and VCA Animal Hospitals. This page covers what comes before that moment: why hot cars are dangerous, the never-do list, planning for a heat wave, and which gear helps. If your pet is already showing emergency signs, stop here and go to that page now.
Act Now: A Pet Left in a Hot Car
A parked car turns into a trap faster than most people believe, and cracking the windows doesn’t fix it.
AVMA publishes a table of how much hotter the inside of a parked car gets over time. Read it together with the footnote directly beneath it, because that footnote sets the scope:
| Elapsed time |
Interior temperature rise |
| 10 minutes |
About +19°F |
| 20 minutes |
About +29°F |
| 30 minutes |
About +34°F |
| 60 minutes |
About +43°F |
| 1–2 hours |
About +45–50°F |
| 2–4 hours |
About +50–55°F |
“*Temperature rise is basically the same, whether 70 or 110 degrees outside.” (AVMA’s footnote to that table.)
That footnote matters most standing next to a car in August: these are not mild-day-only figures. AVMA says that on a 70-degree day the interior passes 110 degrees. On a 95°F afternoon the same one-hour rise of 43°F puts the interior near 138°F; that figure is arithmetic on AVMA’s table, not one AVMA prints. On cracking the windows, AVMA is unambiguous: “cracking the windows makes no difference”. On shade, its warm weather page instructs: “Never leave a pet in the car, even in the shade or with windows cracked.”
Cornell’s Riney Canine Health Center says the same in its own words: even at 70°F outside, the temperature inside a car can climb by 40 degrees in an hour, and most of the rise comes in the first 15 to 30 minutes. AVMA attributes the underlying numbers to research on vehicle safety for children, not to its own study.
This table describes a parked, unattended car with nothing cooling the cabin. A stopped car in mass-evacuation traffic is different while the engine and air conditioning are running, but it turns into this same curve the moment you shut down to save fuel. Our stuck in evacuation traffic guide covers that shutdown decision, including how to budget fuel as climate control rather than distance.
If you find a pet showing heat-stress or heatstroke signs in a car, treat it as the heatstroke emergency it is. The first move depends on whose car it is:
- If the car is yours, or the owner is standing there to open it, get the animal out of the vehicle and into shade or air conditioning immediately. There is no waiting step, and every minute counts.
- If it is a stranger’s locked car, the call comes before the glass. Dial 911 or your local animal control first, and say the animal is in distress, because that moves a request up a queue. Of the six hot-car statutes covered in our guide to breaking a car window to save a dog, by state, five reach a private person at all, and every one of those five conditions its protection on contacting law enforcement, animal control, the fire department or 911. Wisconsin, Indiana and Massachusetts require that contact before the entry on the face of the text; Florida accepts it before entry or immediately after; Ohio requires a good faith effort beforehand and allows contact afterward only where prior contact was not possible. Getting the animal out first and sorting the call out afterward is the ordering those three states do not protect. That guide quotes each statute and shows you how to open your own state’s.
- Once the animal is out, whether you or a responder got it out, begin cooling and get to a vet following the steps on our heatstroke response guide: that page has the full, sourced cooling sequence and the “stop reading, go to the vet” signs.
- A state appearing on a hot-car law list is not the same as that state authorizing you. As of 2025, the Animal Legal Defense Fund counts 32 states plus DC and Guam with some form of hot-car law, split across three types: laws restricting confinement that endangers an animal, laws giving police or other officials rescue authority, and, in a smaller subset of states, civilian “Good Samaritan” rescue protections. A state can be on that list because it authorizes officials only. Coverage differs by state and changes over time, so check your state’s current statute and call local animal control or non-emergency police rather than assuming a protection applies to you. And the immunity is narrower than the label: ALDF says most Good Samaritan laws “only provide civil immunity, but not criminal immunity,” and that unless the law provides criminal immunity, rescuers could still be prosecuted for property damage, trespass, or any other applicable crimes.
If you suspect poisoning alongside heat distress, the ASPCA Animal Poison Control Center is staffed 24 hours a day at (888) 426-4435 (a consultation fee may apply); this is a poison-specific line, not a general emergency number.
The Never-Do List
These are named, sourced dangers, not general caution. Each one has caused preventable heatstroke deaths.
- Never leave a pet unattended in a parked car, for any amount of time. AVMA’s instruction has no exception in it: “Never leave your pet alone in a parked vehicle, no matter what the outdoor temperature or how long you think you’ll be gone.” There is no safe duration once outside temperatures are warm enough to matter.
- Don’t rely on shade alone to make a parked car safe. AVMA’s instruction has no shade exception either, and its vehicle page says a vehicle can quickly reach a temperature that puts a pet at risk of serious illness or death even if the car is left in the shade. AVMA does not say shade buys a pet time, so do not plan on it.
- Don’t exercise or work a pet during peak heat. AVMA says overweight pets and short-nosed dog breeds carry higher risk of problems with warm-weather exercise. It also says not to walk, run, or hike with a dog during the hottest parts of the day or on particularly warm days, so shift walks and activity to early morning or evening.
- Don’t ignore hot pavement. Asphalt and dark pavement can be far hotter than the air above it. Cornell’s Riney Canine Health Center recommends a simple check: if you can’t hold your hand, or stand barefoot, on the pavement for about 10 seconds, it’s likely too hot for your dog’s paws. Walk on grass or dirt instead when the pavement fails that test.
- Don’t assume a fit, average-size, non-flat-faced dog is low risk. The ASPCA says elderly animals, overweight animals, and animals with heart or lung disease should be kept in air-conditioned rooms as much as possible during heat, and flat-faced breeds (see below) carry elevated risk even at moderate temperatures.
- Don’t wait for emergency signs to act. AVMA’s heat-stress warning list (anxiousness, excessive panting, restlessness, excessive drooling, unsteadiness, abnormal gum and tongue color, collapse) is your cue to act immediately, not a “watch and see” list. Sign-by-sign guidance and cooling steps are on our heatstroke page.
Brachycephalic and Higher-Risk Pets: Flag This Early
Flat-faced (brachycephalic) breeds can’t pant as efficiently as longer-nosed animals, and panting is a pet’s primary way of shedding heat. The ASPCA names Pugs and Persian cats as more susceptible to heatstroke for this reason. Cornell’s Riney Canine Health Center adds Bulldogs, Boston Terriers, and Boxers to that list, and notes these breeds are at higher risk in hot or humid weather, not just extreme heat.
Beyond breed, both the ASPCA and Cornell name the same additional risk factors:
- Senior or elderly age
- Being overweight
- Heart or lung (respiratory) disease
The ASPCA’s guidance for these higher-risk pets is direct: keep them in air-conditioned rooms as much as possible during a heat wave. If your pet fits any of these categories, build your heat wave plan (below) around that risk from the start.
No source cited here publishes a numeric humidity threshold. High humidity impairs the evaporative cooling panting is supposed to provide, so treat a hot and humid day as higher risk than a hot, dry one at the same air temperature.
Planning Ahead for a Heat Wave
Prevention beats response. A few habits, done before the heat wave hits, cut your risk of ever needing the emergency steps above.
Check a forecast tool built for this, and read what it says. The National Weather Service’s HeatRisk tool, run by NOAA’s Weather Prediction Center and labelled experimental on its own page, gives a 7-day forecast in five categories:
- Green: little to no risk from expected heat.
- Yellow (minor): primarily affects those extremely sensitive to heat and without cooling or hydration.
- Orange (moderate): affects those sensitive to heat, especially without cooling or hydration, and some health systems and industries.
- Red (major): affects anyone without cooling or hydration, as well as health systems and industries.
- Magenta (extreme): rare or long-duration extreme heat with no overnight relief, affecting anyone without cooling or hydration, as well as health systems, industries, and infrastructure.
NWS writes every category in terms of people, not animals. Treating a heat-sensitive animal as at least as exposed as the people each category describes is this site’s reasoning, not a threshold NWS publishes. Use HeatRisk alongside official NWS heat watches, warnings, and advisories to plan which days to keep outdoor time short.
Shift the clock, not just the destination. Move walks, yard time, and errands that involve the car to early morning or evening, when both air and pavement temperatures are lower. This addresses the pavement-burn and exercise risks in the never-do list above.
Never plan around “I’ll just leave the AC running” as a hot-car solution. A running car with AC left unattended carries its own risks (mechanical failure, someone bumping the gear shift, a thief) and doesn’t change the core rule: AVMA’s guidance is never to leave a pet unattended in a parked car, full stop.
Build heat into your existing emergency kit. If you already have a pet go-bag or evacuation kit, add a collapsible water bowl and check that your pet’s ID tag and microchip info are current before heat wave season, so a heat-related escape or separation doesn’t compound into a second emergency. Our pet emergency kits coverage has the full checklist if you’re starting from zero.
Know your at-risk pet’s plan before a heat wave, not during one. If your pet is brachycephalic, senior, overweight, or has a heart or lung condition, decide now which days you’ll skip outdoor time entirely, based on the HeatRisk categories above, rather than making that call in the moment.
Want the go-bag list on paper before heat wave season? Get the free printable go-bag checklist.
Gear That Actually Helps (and Gear That Doesn’t Solve What It Looks Like It Solves)
EmergencyPetPrep is reader-supported. If you buy through links on this page, we may earn a commission at no cost to you. Our picks are based on manufacturer specs and published guidance, never on commission. As an Amazon Associate I earn from qualifying purchases. We don’t sell or test this gear ourselves; every spec below comes from the manufacturer’s own product page, cited by name, and every price is a tier, not an exact figure, per our review methodology. Brand names below are trademarks of their respective owners; EmergencyPetPrep is not affiliated with or endorsed by them.
A cooling or airflow product’s job is to reduce heat stress during safe, supervised activity. None of the products below are a hot-car solution, and none replace shade, air conditioning, or the vet. The Green Pet Shop’s own product page is explicit that its cooling pad is not for direct sun, hot air, or car use, and that warning generalizes: no consumer cooling gear is rated to make a parked car safe.
The gear that reduces real, everyday heat-wave risk is unglamorous. A cooling mat gives an indoor or shaded dog a comfortable place to rest. A soak-and-wear vest actively pulls heat off a dog on a supervised outdoor outing. For which of those two to reach for first in a heat emergency, our cooling vest vs. cooling mat comparison weighs them head to head. A cellular temperature monitor is a backstop for the rare, unavoidable situation where a pet is briefly in a vehicle (never a reason to feel safer leaving one unattended). A collapsible bowl prevents the dehydration that makes heat stress worse. A battery-powered crate fan adds airflow to a shaded or indoor crate when there’s no power station to run a box fan, though it only circulates air and never cools it below the room’s temperature. A 12V clip-on car fan does the same airflow job for a pet riding in the car with you, running off the vehicle’s own 12V outlet, and it too only moves air rather than cooling it below the cabin temperature. A reflective windshield sun-shade lowers how hot an empty, parked cabin gets before you load a pet for a drive, but reflection only delays the heat and never makes an unattended parked car safe. None of them substitute for the never-do list above.