Is it safe to?Reviewed: 2025-12-27~1 min

Is it safe to drink water left in a hot car?

Short answer

⚠️Depends / use caution

It depends — sealed water in a clean, heat-stable bottle for a short time is usually fine, but prolonged heat or questionable containers make it risky.

Why people ask this

Cars can get extremely hot, and people worry about chemicals leaching from plastic and bacteria growing in bottles left for hours or days. They want to know if the water is still safe to drink or should be tossed.

When it might be safe

Sealed, unopened bottle left for a few hours and water tastes/looks normal
Stored in a stainless steel or glass bottle without damaged seals
Brief exposure (e.g., an afternoon) rather than days of heat cycling
Bottle and cap are intact with no warping, discoloration, or odors
Previously cleaned reusable bottle with no backwash (no prior drinking from it)

When it is not safe

Reusable or disposable plastic bottle left for days in high heat or sun
Bottle is deformed, cloudy, or has a plasticky/chemical odor or off taste
Previously sipped bottle (backwash) that was warm for many hours
Unsealed or partially open container exposed to the car environment
Visible growth, particles, or residue inside the bottle or cap

Possible risks

Chemical leaching from certain plastics when heated (e.g., antimony, BPA/BPS alternatives, phthalates)
Bacterial growth in bottles that have been drunk from and then warmed
Microplastics increasing with heat and plastic wear
Off flavors and odors indicating degradation or contamination
Very hot water potentially causing mouth discomfort or minor burns

Safer alternatives

Use an insulated stainless steel bottle and keep it closed
Store water in a small cooler or insulated bag if it must stay in the car
Discard questionable water and refill from a safe source
Keep spare sealed bottles in shade and rotate them regularly
Bring water with you instead of leaving it in the vehicle when possible

Bottom line

If the bottle is sealed, intact, and only briefly heated, it’s likely fine; when in doubt—especially with plastic left in high heat or bottles you’ve drunk from—discard and use fresh, properly stored water.