Why Idaho Power Says You Should NEVER Leave Water Bottles in Your Car

When the Weather Channel released their summer temperature outlook for 2025, Idaho was one of the states expected to see above average temperature throughout the entire summer. So far, it looks like that prediction is right on. Boise’s about to bake! 

Our area is about to head into a stretch of days with forecasted highs that are 10-15º above average, including a scorching 104º day on Tuesday, July 1. While that’s not quite hot enough to establish a new record high for the date (110º) it is hot enough for the National Weather Service to issue a Heat Advisory for parts of southwest Idaho and southeast Oregon. 

READ MORE: 11 Things You Should Never Leave in Your Car on a Hot Idaho Day

The heat advisory comes with the usual reminders like staying indoors in air-conditioned spaces, checking up on elderly neighbors and relatives, limiting strenuous activity during the hottest parts of the day and drinking plenty of fluids. 

But there’s one summer danger, Idahoans forget about it all the time and it’s the plastic water bottle you left in your cup holder. 

Idaho Power Video Reveals Plastic Water Bottle Danger

I’ll admit it. My car is basically a trash can on wheels. There’s a lot of junk on my passenger seat, my back seat and the floor. Without going to check, I guarantee that there are at least three disposable water bottles in my vehicle. Does this sound like your car too?

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Then let this video from Idaho Power be a reminder to go remove them. Originally shot in 2017, one of the company’s battery techs explains what happened while he was eating lunch in his truck. He looked over and noticed smoke coming off the passenger seat where he had tossed a full plastic water bottle. 

The sunlight shining through the window focused to a single point as it refracted through the bottle. It’s a lot like the science class lesson where your teacher showed you how to burn through newspaper using a magnifying glass.  

When the tech realized it was seat smoking, he moved the bottle and discovered two small burn marks on the seat. 

Idaho Power decided to use the incident as a teaching moment and tried to recreate what happened. A non-contact thermometer showed that the seat beneath the bottle reached 213º. 

Years later, a Central New York fire department showed a local TV station how water bottles could start a fire inside your car. He said this is more likely to happen in places where there is low humidity and dry heat.

Idaho just so happens to be famous for both of those things, so let this be a friendly reminder to clean out your car before it turns into a mobile fire hazard!