The Cool List – 16 Items that should Never be left in a Hot Car

Although not many people like the cold, people forget that excessive heat in your vehicle can be truly punishing. Enclosed spaces, such as your car’s interior cabin, can become like an oven during the daytime. Especially if you are parked in an exposed position, and have not been able to find the shade.

As the inside temperature of your car can climb several degrees higher than the ambient temperature, it’s wise to be careful about what’s left in the car on a summer’s day. Check our list of vulnerable things that should not be left in the car, to avoid a potentially troublesome or dangerous situation. Yes, there are some obvious inclusions to our list; but also some you might not have heard before…

Our List of Items

Whilst not exhaustive; this is our list of no-go items that you should avoid leaving in the car on a hot day. If you must carry them, then take care and try to leave them in a darkened part of the car or if applicable, a cool box.

1. Sunscreen

Whilst this body rub will help keep the sun from damaging your skin, it does tend to lose effectiveness as it gets warmer. In worst case scenarios, it could even explode.  Got an old bottle in the glove box? It’s probably not doing the job it used to. Chuck it and get a new one.

2. Food

Heat rapidly speeds up the decomposition of food. Especially those items that need to be left in the fridge. Whilst your sandwiches might survive in the cold box for a few hours, delicate items like eggs, milk, meats and soft cheese will quickly ruin if left in a hot car. Pet food is equally as vulnerable; if it goes bad from the heat in your car it could give your pet an unwanted upset stomach – or worse.

3. Bottled Water

Can actually act as a lens, refracting sunlight into a point and causing your interior to burst into flames. Also, plastic bottles can leak tiny plastic particles into the water when the bottle gets hot – these can cause harm if these particles build up in your body.

4. Wine

Exposure to sunlight can cause wine to go bad, forming a compound known as ethyl carbonate in your drink. Not only will this sour your entire bottle, but has also been linked with cancer in humans.

5. Pets

Never, ever leave your pets in the car. Animals can suffer from heatstroke even when left for short periods of time with the window open.  Dogs are especially prone to overheating – symptoms of which include excessive panting, tiredness and drowsiness and vomiting in the worst cases. If your dog starts suffering from any of these, then it needs to be taken somewhere cooler immediately.

6. Children

Even when the temperature doesn’t seem too aggressive outside, in-car temperatures can quickly climb to several degrees above the outside ambience. Children, much like pets, can rapidly overheat leading to heatstroke and dehydration. At best this will lead to tears and frustration, at worst, you could be looking at a hospital visit. No matter what the hassle might be – take your kids out of the car with you.

7. Aerosol cans

Pressurised spray cans, such as cleaner sprays, hair spray, deodorant or anything are very prone to heat. Check the side of the can and you’ll see a recommended storage temperature. As the can heats up in a hot car, the contents will expand, leading to cracks or damage in the container, or in some severe cases, the contents can even explode.

8. Plants

Returning from the garden centre? Make sure your new green purchase survives the heat and the trip. Even short journeys in the back of the car with the boot shut can damage your young plants. Instead keep them in the back of the car, shaded by a little paper or cardboard, and a cooling draft of air from the AC or an open window.

9. Batteries

These handy power cells are also vulnerable to the heat. Batteries contain strong acids and corrosive materials that can damage your skin on contact or your lungs if breathed in. If left in a hot car for too long, the containers can crack and melt, allowing these chemicals to seep out.

10. Disposable lighters

Much like aerosol spray cans, disposable lighters contain gas under pressure. If the heat gets to them, they can explode, cracking windows or breaking internal fixtures whilst spreading flammable fluid all over your car, which could potentially catch fire.  

11. Fizzy drinks in cans

Again, you’re looking at pressurised liquids in thin metal containers – a familiar story by now. Soft drink cans are not immune to the heat, and can explode in the car. Even if the can rupturing doesn’t cause damage, then cleaning your car when it’s covered in sticky, sugary liquid is still a nightmare. Additionally the heat can make them spoil and go rancid.

12. Smartphones

Even though smartphones are designed to operate at quite high temperatures, when you leave a phone in the sun, this can push it above the safe operating temperature. Whilst the phone is unlikely to explode, the fine electronics and the battery can be damaged beyond repair by the heat.

13. Sunglasses

A favourite driving essential, sunglasses keep the sun out of your eyes when you’re behind the wheel. However, the fixings, frames and even cheaper lenses can all warp, discolour and even fracture in the heat, leaving your eyes without a sun shield when on the road. Do the right thing and put them in a case in a darkened part of the car.

14. Medications

Most medicines have safe storage temperatures, and due to the mix of chemicals in their composition, should not be exposed to excess heat. Even paracetamol and ibuprofen can spoil in the heat and your antihistamines can perish. Be also aware that some essential lifesaving medicines (EpiPens for example) can become completely useless if they reach certain temperatures.

15. Lipstick

Lipsticks are already soft and malleable. Leave one in the car and it’s likely that it will melt, leaking through the casing and leaving a puddle of waxy, thick colour somewhere unwelcome in your car’s interior.

16. Wet beach clothes

Whilst it may be tempting to leave damp beach clothes in the back of the car for the next time you visit the beach or pool, damp clothes can quickly develop mould and yeast. You might find that the convenience of leaving the boardshorts or bikini in the back of the car soon leads to a more inconvenient itch.

Our Final Word

Of course, one of the ideal moves is stopping your car from overheating in the summer. Take stock of what you’re carrying, and leave the non-essentials at home to stop them from getting affected by the heat. As with most things in life; a little planning in advance can prevent a lot of problems in retrospect.