10 items you should never leave in a hot car
A car parked in direct sunlight on an 80°F day can hit 120°F inside within an hour, and dashboard temperatures climb past 165°F on a 95°F afternoon, according to research from Arizona State University’s heat-health team.
That kind of heat damages belongings, spoils food and medication, and in some cases creates a serious fire risk. Here are 10 things to always take with you when you park.
1) Aerosol cans
Hairspray, deodorant, sunscreen sprays, dry shampoo, and spray paint are pressurized and typically tested to withstand 120°F – a threshold easily exceeded in a parked car. Incidents of cans rupturing inside vehicles, sometimes shattering windshields, are reported every summer by U.S. fire services.
2) Medication
The FDA recommends storing most medications between 68°F and 77°F. Insulin loses potency rapidly above 86°F and is effectively destroyed above 98°F – a serious concern for the roughly 8 million Americans who depend on it.
A 2024 stability study published in the Journal of Allergy and Clinical Immunology found that EpiPens lost 41.6% of their epinephrine potency after three months at 122°F – a temperature easily reached inside a parked car. Inhalers, antibiotics, thyroid medication, and birth control are also temperature-sensitive.
3) Sunscreen
Heat breaks down active ingredients like avobenzone, meaning the SPF you think you’re applying may be substantially lower than the label claims. The FDA warns that sunscreen stored above 100°F for extended periods may be ineffective before its printed expiration date.
4) Food and groceries
The USDA’s bacterial “danger zone” is 40°F to 140°F, and perishables shouldn’t sit in that range for more than two hours — or one hour above 90°F ambient. Inside a hot car that window shrinks to minutes. Sealed soda cans can also rupture from internal pressure, and chocolate, eggs, and dairy spoil within a short drive home.
5) Eyewear
Plastic frames warp permanently above 130°F. Polarized, photochromic, and anti-reflective lens coatings can bubble, crack, or delaminate after a single afternoon on a dashboard. Optometrists routinely see ruined prescription lenses every summer.
6) Lighters and matches
Disposable butane lighters can rupture or explode when their internal pressure rises in extreme heat. There are documented cases of lighters left on dashboards igniting and starting vehicle fires.
7) Glasses cases and clear water bottles
This one surprises people. A clear plastic water bottle or a magnifying glasses case can act as a lens, focusing sunlight onto upholstery or paper and igniting it. Fire services in several U.S. states have demonstrated this effect, with temperatures at the focal point measured above 200°F.
8) Important documents
Passports, Social Security cards, and laminated IDs warp, bubble, and fade in extreme heat. Ink on thermal-printed receipts and tickets can vanish within hours of direct sun exposure.
9) Pets and children
According to NHTSA and KidsAndCars.org, an average of 38 children die in hot cars in the U.S. every year, with 2018 and 2019 tied as the worst years on record at 53 deaths each. Since 1990, more than 1,170 children have died this way. A child’s body heats three to five times faster than an adult’s.
The American Veterinary Medical Association reports that on a 70°F day — not even hot by most standards — a car’s interior can reach 89°F within 10 minutes and 104°F within 30 minutes. In 29 states, bystanders are now legally permitted to break a window to rescue a trapped pet under certain conditions. Never leave a child or animal in a parked car, even briefly, even with the windows cracked.
10) Lithium-ion devices
Lithium-ion devices such as vapes, phones, laptops, power banks, and e-bike batteries is one of the fastest-growing fire risks in American homes and vehicles. Lithium-ion cells are designed to operate safely up to around 140°F, well below the temperature a dashboard reaches on a summer afternoon. Sustained heat exposure can cause cells to swell, leak, or enter thermal runaway — a self-sustaining chemical reaction that can ignite a fire reaching over 1,000°F in seconds.
The scale of the problem is growing fast. In 2025, Anker recalled more than 1.1 million PowerCore 10000 power banks for overheating risks, followed by a second recall of around 481,000 additional units across six more models just months later.
The FAA has verified more than 600 lithium-battery incidents on U.S. aircraft since 2006, with a record 89 incidents in 2024 alone — averaging more than one a week. Vape and e-cigarette devices accounted for 15 of those 89 incidents, more than laptops or cell phones. Conditions inside a hot car are far worse than a pressurized aircraft cabin.
Don’t miss these lithium battery warning signs
Shane Margereson is owner of Ecigone, and works with lithium batteries every day. He says that the warning signs are often missed:
“The battery in your vape is the same type as the one in your laptop, your power bank, and your e-bike — and they all react to heat the same way. Watch out for swelling, a sweet chemical smell, discoloration, or the device feeling warm when you haven’t used it.
“If you spot any of those, stop using it, keep it somewhere non-flammable, and take it to a battery recycling point. Never put a damaged lithium battery in the regular trash; that’s how landfill and garbage-truck fires start. And the simplest rule of all: treat it like your phone. Never leave it on the dashboard, in the glovebox, or in direct sunlight.”
