On a scorching afternoon, direct sunlight and limited ventilation can make a parked car substantially hotter than the surrounding air. The cabin can become a hazardous heat environment, putting people and pets at risk, along with heat-sensitive belongings. The New York City Department of Health and Mental Hygiene notes that about 80% of heat-stroke victims in the city are overcome by excessively hot conditions in their own homes, a reminder that dangerous heat exposure is not limited to outdoors or vehicles.
Heat can also affect items left inside a vehicle, but the risks differ. People can suffer heat illness, while batteries can be damaged or fail and flammable products can contribute to a fire if exposed to ignition sources. These hazards are reasons to take precautions, not evidence that every forgotten item will ignite or explode.
Pressurized Containers and Lighters
Aerosol products, including deodorants, hair sprays, insecticides and some cleaning products, are pressurized, and their labels provide handling and storage instructions. Avoid leaving them in direct sunlight or in a hot vehicle when possible. A plastic lighter is also best taken with you rather than left in a hot cabin, but a forgotten lighter should not be treated as certain to explode. Federal transportation rules restrict flame-producing devices in specified commercial vehicles carrying certain hazardous materials; those provisions are not a blanket consumer-storage rule for private cars.
Electronics and Batteries
Phones, power banks, laptops, tablets and e-cigarettes commonly contain lithium-ion batteries. Heat alone does not mean a battery will catch fire, but a damaged or overheating battery can present a fire risk. St. George City, Utah, identifies overheating, swelling, unusual smells, leaks, smoke, hissing and popping as warning signs of battery damage, and cautions that a damaged battery can overheat and start a fire. If a device shows these signs, do not use or charge it; keep clear and follow local emergency guidance.
Sunlight and Combustible Materials
Items on a dashboard can be exposed to direct sunlight and heat. Keep combustible materials away from ignition sources: a federal mine-safety regulation states that heat sources capable of producing combustion must be separated from combustible materials when a fire hazard could result. That rule applies to mining operations, not passenger cars, but the underlying precaution is relevant. Avoid treating transparent bottles, perfume flasks or glasses as automatic fire starters.
Prevention and Practical Advice
Before locking the car, check the cabin and take electronics, aerosol products, lighters and other heat-sensitive belongings with you when practical. Storing an item in the boot may shield it from direct sunlight, but it can still become hot inside a parked vehicle. Follow product-label storage instructions and never leave a person or pet in a parked car during hot weather.
Fire risks in vehicles are not unique to Spain. Across Europe, authorities are adapting regulations and public messaging to address the dangers posed by extreme temperatures and modern technology. For example, some countries have introduced measures to encourage safer driving and reduce emissions, such as Austria's policy allowing electric cars to bypass certain speed limits on highways, a move that highlights the developing relationship between vehicles, safety and environmental concerns (see how Austria is changing highway rules for electric vehicles).
Removing heat-sensitive and potentially hazardous items from a parked car is a straightforward precaution that can reduce the chance of damage and help protect people and property during hot weather.
