1. People and pets
Even on a day with cooler temperatures, children and pets in cars are still at risk, as the temperatures inside a parked car can still spike to life-threatening levels, according to a 2005 study by the Stanford University School of Medicine. "There are cases of children dying on days as cool as 70 degrees Fahrenheit," lead author Catherine McLaren, MD, clinical instructor of emergency medicine told Stanford Medicine.
Even if you're running into a store for a single item or even just to drop off a pre-stamped letter at the post office, if something unexpected comes up and prolongs your task, you just put the living thing left behind at grave risk.
2. Medicine
Extreme heat can reduce the efficacy of certain medicines, Dr. Sarah Westberg, PharmD, an associate dean at the University of Minnesota College of Pharmacy, told NPR.
"Pharmaceutical manufacturers recommend most of their products be stored at a controlled room temperature of 68 to 77 degrees," Dr. Skye McKennon, PharmD, told the New York Times.
When you get out of your car, you're better off taking your medications with you than leaving them.
3. Plastic water bottles and food containers
If you leave plastic food or drink containers in a sweltering car, you could end up ingesting something harmful. Plastics can leach various potentially dangerous substances into their contents, including BPA, which may alter hormones over time and potentially increase risk for certain endocrine disorders.
4. Phones, tablets, computers, and other tech
If you read the manual for your phone, tablet, laptop, or other cherished (and likely expensive) electronic device, you may have come across the recommendation to avoid exposing the hardware to high temperatures.
Placing your device in direct sunlight can have damaging consequences to the battery, especially if it has a lithium-ion battery. According to Apple, temperatures higher than 95 degrees Fahrenheit can irreversibly damage the battery capacity of your iPhone, iPad, or MacBook.
5. Sunscreen
If you thought you were being responsible by always keeping sunscreen at the ready in your car during the summer months, unfortunately, you have to think again.
The sunscreen you rely on to protect your skin can be rendered less effective by heat — and there’s no shortage of that in a car during the summer.
"When sunscreen is stored in a high temperature, the effectiveness decreases, and the sunscreen becomes less stable and reliable. When it gets hot or is stored above 77 degrees Fahrenheit, the potency is destroyed, and the sunscreen will degrade," cosmetic dermatologist Dr. Fredric S. Brandt, MD, told Refinery29.
6. Booze
Leaving a six pack of your favorite porter or a nice cabernet in a hot car is a great way to end up with six skunked beers and a ruined bottle of wine.
The sun's rays break down acids in beer, and the compounds that result bind with sulfur proteins, giving it the dreaded "skunked" taste, as Business Insider previously reported.
For wine, too much exposure to heat can cause reds to take on a "tangy, astringent character," certified sommelier Laura Burgess wrote for VinePair.
7. Chocolate
If you have ever tried to clean melted chocolate off of clothing, then you know it's also a good idea to keep the stuff away from upholstery — not to mention the electronic components of your car.
According to Lindt, chocolate has a melting point of only about 79 degrees Fahrenheit (which is why candy bars melt in your pocket). It can turn into an absolute mess of gooey liquid in a hot car.
8. Crayons
Just like chocolate, crayons have a relatively low melting point. And like chocolate, they make an absolute mess when they turn into goo. According to Crayola, these colorful sticks begin to soften at 105 degrees and will liquefy at temperatures above 120 degrees. So make sure the kids clear out their car entertainment after each drive.
9. Pneumatic tires
If you're a cyclist, a scooter enthusiast, or have a stroller with pneumatic tires, which are air-filled tires that you use a pump to inflate, don't leave that gear in the car on hot, sunny days.
According to The New York Times, high heat can cause the air inside the tire to expand, potentially resulting in a blowout. High temperatures can also potentially weaken the rubber, causing a flat tire.
10. Glasses
Keeping a pair of sunglasses in your car is a good practice, right? Well, not if they're a pricey or prized pair. The heat from the car can distort the frames, damaging the fit and function, and can even warp the lenses.
