Is it OK to leave bottled water in a hot car?

Quick Answer

It’s generally not recommended to leave bottled water in a hot car for extended periods of time. The heat can cause the water to become contaminated with chemicals from the plastic bottle. However, if the bottle is only in the car for a short time, the water should be safe to drink. The plastic may impart a slight plastic taste, but it won’t be harmful.

Does Heat Affect Bottled Water?

Yes, heat can affect the quality and safety of bottled water:

  • It can cause plastic chemicals to leach into the water – Prolonged exposure to high temperatures can cause chemicals like BPA and phthalates to leach from the plastic bottle into the water. This could potentially pose health risks if consumed regularly.
  • It alters the taste – Heat can cause subtle changes in the taste of bottled water, imparting a slight plastic flavor. The hotter the temperature, the more pronounced this effect will be.
  • It promotes bacterial growth – Heat accelerates bacterial growth. If bottles contain any pathogens, hot temperatures inside a car could encourage bacteria numbers to multiply faster.

The level of risk depends on the temperature and duration of exposure. Short periods in hot cars are less concerning, while prolonged heat can make the water unsafe to drink.

How Hot Do Car Interiors Get?

Studies have found that car interiors can reach extremely high temperatures, even when outside air temperatures are only moderately hot:

  • On an 80 degree F day, car interiors can reach 99 to 123 degrees F
  • At 90 degrees F outside, car interiors may reach as high as 160 degrees F
  • Interior temps can spike more than 40 degrees F above outdoor air temps

The greenhouse effect causes radiant heat to become trapped inside a closed vehicle, sending temperatures soaring. Sunlight shining through windows also heats the interior surfaces like dashboards, seats, etc.

These surfaces then continuously re-radiate the accumulated heat outwards throughout the car interior. Cracked windows do little to relieve these extreme temperatures.

Is It Safe to Drink Bottled Water Left in a Hot Car?

Up to 1 Hour in a Hot Car

Water bottles left in a hot car for up to one hour should still be safe to drink, although taste may be slightly affected.

Studies show that plastic bottled water reached temperatures between 88-100°F after sitting in a closed parked car for one hour on a 90°F day. This brief, moderate heat exposure poses minimal risks of:

  • Chemical leaching – An hour is generally not long enough for concerning levels of plastic chemicals like BPA to migrate into the water.
  • Bacterial growth – One hour provides limited opportunity for bacterial multiplication. Normal bottled water has low bioburden.

The water may pick up a subtle plastic flavor, but this is not harmful. The bottle shape may become slightly distorted as well. Overall, the water should still be safe for consumption after 1 hour inside a hot car.

2-6 Hours in a Hot Car

After 2-6 hours inside a hot car, bottled water safety becomes more questionable.

Studies have measured water temperatures up to 126°F in this timeframe. With extreme heat and longer duration, risks increase of:

  • Chemical contamination – More time allows for chemical migration from the plastic bottle into the water. One study found antimony levels increased by 90% in PET bottled water after 6 hours in a hot car.
  • Bacterial growth – With ideal bacterial growth temps reaching 105-110°F, 2+ hours could allowReplication of some pathogens, if present.

While likely low risk for most people, sensitive populations like pregnant women and immunocompromised individuals may want to avoid drinking bottled water left for extended periods in hot cars as a precaution. Taste impairments become more noticeable as well.

8+ Hours in a Hot Car

Leaving bottled water in a hot car for 8+ hours is risky and not recommended.

Studies have measured interior car temperatures up to 172°F after 8 hours in summer heat. At these extreme temperatures for prolonged periods:

  • Plastic chemical contamination is highly likely – High levels of antimony, BPA, DEHP and other chemicals have been found in bottled water stored for days in hot cars.
  • Bacterial growth is probable – 8+ hours provides ample time for bacteria like E. coli or Salmonella to rapidly multiply if present.

The water may take on a strong plastic taste and smell. The bottle shape may become very distorted as well, indicating heat damage to the plastic.

With high risks of contamination, it is best to discard bottled water left for 8 or more hours inside a hot vehicle. The increased potential for toxins and pathogens make it unsafe.

Tips for Keeping Bottled Water Cool

To avoid excessive heat exposure when transporting bottled water by car:

  • Park in shade – Choose shady spots to keep car interiors cooler.
  • Use reflectors – Windshield reflectors can block sunlight from heating the interior as much.
  • Insulate bottles – Wrap bottles in towels or store in a cooler with ice packs.
  • Limit time in car – Don’t leave bottles in the car longer than necessary.
  • Check for temperature spikes – Feel bottles to detect unacceptable warming.

Taking simple precautions allows you to keep bottled water at safe, cool temperatures when temporarily storing it in a vehicle.

Should You Drink Bottled Water Left in a Frozen Car?

Bottled water that has been left in a frozen vehicle poses no safety risks. However, you may notice some effects on the bottle and water:

  • Bottle may crack or distort – Freezing temps can damage plastic bottle integrity.
  • Water expands when frozen – You may see ice inside bottle or pushing out the sides.
  • Water tastes different after thawing – It may pick up a plastic taste from the bottle.

Despite these changes, frozen bottled water won’t become contaminated or unsafe to drink. Discard any visibly cracked or damaged bottles. Let frozen water thaw completely before opening to avoid spills. The water should return to normal once thawed and briefly aired out.

Can Temperature Extremes Damage Bottled Water Nutrients?

Bottled waters that contain added vitamins, minerals or electrolytes generally use stable forms that can withstand some temperature fluctuations without degrading.

However, over time, extreme high or low temperatures can start to impair stability of some water nutrients like:

  • Vitamin C – Sensitive to heat, light and air exposure. Degrades faster at high temps.
  • Vitamin B9 (Folate) – Decomposes with prolonged heating or freezing.
  • Probiotic cultures – Live bacteria perish after prolonged freezing or heating.

For waters with added health boosters, try to avoid leaving them for days at extremely high or low temperatures to get the most nutrient benefit. But brief exposures to hot/cold won’t instantly deplete nutrients.

Does Bottle Material Affect Heat Resistance?

The type of plastic used to bottle water can impact how quickly heat causes chemical leaching. Studies indicate:

  • PETE (polyethylene terephthalate) – Most common bottle material. Relatively stable, but can leach antimony and acetaldehyde.
  • PC (polycarbonate) – Leaches BPA most readily with heat exposure. Avoid if concerned.
  • HDPE (high-density polyethylene) – More heat resistant and less prone to leaching chemicals.

Glass bottles offer the most heat protection compared to plastics. But they’re heavy and can shatter if frozen then heated.

Look for HDPE or PETE bottles with labels like “BPA-free” if trying to minimize chemical leaching risks from heat.

Does Bottled Water Go Bad After Expiration Dates?

Bottled water itself does not go “bad” or become unsafe to drink after its printed expiration date. The dates mainly indicate best quality rather than safety.

Unopened, commercially bottled water has an indefinite shelf life when stored properly. The water doesn’t spoil or degrade over time.

After opening, bottled water should be used within 6 months as bacteria or molds can grow in the bottle over time.

Expiration or “use by” dates on water bottles reflect more about potential plastic bottle degradation than the water itself. The plastic may eventually start leaching chemicals with prolonged storage.

High heat accelerates plastic breakdown. So expired bottled water stored long-term in hot places may have greater risks. But otherwise,expiration dates on water bottles relate more to quality than actual spoilage.


While bottled water is generally safe at moderate temperatures, exposure to extreme interior heat inside cars can lead to contamination and create health risks if consumed. Leaving bottled water for prolonged periods in hot vehicles is not recommended.

To keep bottled water cool when transporting it in cars, take simple precautions like parking in shade, insulating bottles in coolers, and avoiding leaving it for longer than necessary. An hour or less in a hot car generally won’t cause major issues with bottled water safety or quality. But beyond that time period, heat-related impacts on the water and plastic bottle quickly multiply.

Heating and freezing bottled water may degrade taste, but in most cases won’t make the water unsafe to drink. Discard bottles that are visibly damaged from temperature extremes. When in doubt, apply the sniff test – if heated water smells strongly plastic, it’s best not to drink it. Keeping bottled water out of temperature extremes preserves quality and prevents deterioration of the water and plastic bottle.

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