It's something that I do all the time, but after seeing the video posted by Idaho Power I will never leave a bottle of water in my hot car again. I first saw the video within a blog posted by Delish, it was about an Idaho Power Company employee that left a bottle of water in their hot car and noticed that it was causing a fire.

The light was be refracted through the water bottle and started to catch the seat on fire. You can actually see two burn marks left on the seat by the plastic bottle. Oklahoma firefighters actually conducted a test to see how hot the sunlight magnification can get and they concluded it was 250 degrees.

While the chances of this happening to you are low, taking preventative measures like removing water bottles is always for the best. I guess these results don't shock me as anyone knows who owns a vehicle with leather seats after it has been in the sun for a while those seats can burn your legs too.