During the dry season, there is a high chance that you will want to have a water bottle handy and may even store a few in your car. After all, opening the door of a stiflingly hot vehicle makes you want to take some water instantly.
You should however be careful of this as leaving a water bottle that’s been sitting in the sun all day in your car isn’t the most refreshing way to quench your thirst in the heat. There is even a more dangerous reason for you not to leave a water bottle in your car: It could start a fire.
Logically, it seems impossible for water to cause a fire, but the secret is in the round bottle shape. On a hot day, the sun shines through the window and through the full water bottle.
The water in the plastic bottle acts like some sort of magnifying glass, with the water inside concentrating the light—and its heat—to one spot. The point on the seat where the rays are focused can get hot enough to create flames.
While you may think the description above only seems hypothetical, there has been reported cases of such happening un the United States of America. In a Facebook video from Idaho Power, stations battery technician Dioni Amuchastegui says it happened to him.
Amuchastegui was sitting in his parked car eating lunch when he noticed smoke inside. On taking a closer look, he realized the spot of light under his water bottle was starting to catch fire. “I had to do a double take,” says Amuchastegui. “It was hot enough to start burning a hole through the seat.”
Sure enough, the extreme heat left two little burn marks. Lucky for him, he was able to notice it before it could do any major damage.
To avoid the scary risk of fire, carry your bottle with you instead of leaving it in an overheating car. If you can’t help but keep it inside your car, it is best to store it under a seat so it’s out of the reach of the sun’s rays.