Can Cold Weather Crack a Windshield? Heat, Ice and Defrost

How temperature cracks a windshield

Cold or heat cracks a windshield when one part of the glass is much warmer than another. A uniformly cold windshield is under little stress. The danger is the difference in temperature across the glass, which glass makers call thermal stress.

A windshield is laminated glass: two layers of glass bonded to a plastic interlayer, as Safelite describes it. Pilkington’s technical bulletin ATS-123 says a temperature difference between the center and edge of a pane creates about 50 psi of edge tension for every 1 °F. The bulletin adds that breakage becomes likely once edge tension passes 2,000 to 3,000 psi. By that rule, ordinary untempered glass enters the danger zone at roughly a 40 to 60 °F difference. These are building-glass figures, used here only to show the scale.

Viracon, another glass maker, says damage to the glass “dramatically” lowers its resistance to thermal stress. That is why chips matter more than the thermometer. Rear and side windows are usually tempered glass and react differently, as explained in can cold weather crack a rear windshield.

What NHTSA complaints show about cold and cracks

Most windshield-crack complaints show no seasonal pattern, while the ones that mention cold or the defroster cluster in winter. CarGlassFix counted 5,974 NHTSA owner complaints from 2010 to 2025 that describe a cracked front windshield, sorted by the month of the incident.

Across all 5,974 complaints, 26.9% happened from December to February. That is close to the 24.5% share for every NHTSA complaint in the same files. A subset of 449 complaints mentions cold, snow, ice, the defroster or the heater. Of those, 54.6% happened from December to February and 12.5% from June to August. Many describe a crack appearing soon after the defroster was switched on. Without Subaru, the largest brand in the data, the winter share of that subset is 59.7%. These are unverified owner reports, so they show timing and do not prove the cause.

Why existing chips spread in winter

An existing chip is the most common starting point for a cold-weather crack. Infiniti’s dealer bulletin on windshield cracking says cracks spread from the strike point because of “thermal stresses caused by temperature fluctuation”. It also names vibration, wind force and potholes.

The same bulletin says small scratches in the wiper path can open the outer glass surface. A crack can then grow from thermal conditions, vibration or wind pressure. Safelite adds that water inside a chip expands when it freezes and pushes the glass apart. It also warns against running wipers over ice when damage sits in the wiper path.

Safelite describes the winter mechanism this way: the outer surface cools and contracts while the heater keeps the inner surface warm. The chip is where that tension is released. How fast a crack grows is covered in will a windshield crack spread. If a chip or short crack appears, the size limits in how big a windshield crack can be repaired show whether repair is still possible.

Can the defroster crack a cold windshield?

The defroster can trigger a crack when hot air hits frozen glass that already has damage. No automaker document read for this page says the defroster cracks an intact windshield. Sources differ on how much heat to use, and the condition of the glass explains the difference.

In the CarGlassFix count of NHTSA complaints, 260 windshield-crack reports mention the defroster, defogger, de-icer or heater, and 54.2% of them happened from December to February. Owner reports cannot show whether a small chip was already in the glass when the crack started.

Source	What it says	Applies to
AAA	Set the heater to defrost and move the temperature to full heat to remove ice	Routine ice removal
Safelite	High heat pointed at a cold windshield often makes existing damage spread	Windshields with a chip or crack
Pilkington ATS-123	Vents blowing hot or cold air straight at glass can overstress its edges	Building glass, used for scale
Kia K4 manual	Warm the windshield with the defroster before using the washer in freezing weather	Washer use below freezing
Subaru SB 12-257-25R	Lists cracks starting at the wiper deicer terminal as their own type	Subaru warranty decisions

A damaged windshield calls for gentler heat than an intact one. Subaru’s bulletin calls deicer-terminal cracks an “unrelated cause”. Its basic 3-year or 36,000-mile coverage covers them, while its crack warranty extension does not. Safe defrosting habits are covered in how to make car windows defrost.

Will warm or hot water crack a frozen windshield?

Yes, hot or warm water on a frozen windshield can crack it, and automakers tell drivers not to use it. Mazda’s 2025 CX-5 manual says to never use warm or hot water to remove snow or ice from windows, because “it could result in the glass cracking.”

AAA calls hot water “a no-no” because it can crack glass through thermal shock. AAA also rules out a torch, a metal scraper and tapping the ice with a hammer. The water heats the outer glass surface in one area while the rest of the windshield stays frozen. That local difference creates the edge tension Pilkington describes.

Warm water is no safer in this guidance, since Mazda names both. AAA lists a plastic scraper, the defroster and a commercial de-icer spray as the methods to use. A plastic scraper also avoids scratching the glass, and scratches are crack starters in Infiniti’s bulletin. Preventing ice so the glass needs less heat is covered in how to protect a windshield from frost.

Can heat crack a windshield?

Heat can crack a windshield, usually through a sudden temperature change on glass that is already damaged. Safelite says the outer surface heats faster in the sun than the shaded inner surface, and the uneven expansion stresses any chip.

Safelite names three hot-weather triggers. The first is cold air conditioning blasted at a windshield that has been baking in the sun. The second is cold water poured on hot glass. The third, and the most common in Safelite’s view, is a sun-heated car hit by cold rain. Daily heating and cooling also keeps working on existing damage through the summer.

A laminated windshield rarely shatters from heat, because the interlayer holds the glass together. Safelite calls shattering from heat alone “unlikely”. Tempered side and rear windows break into small pieces instead, as covered in why did my side glass shatter. Other crack causes, including stress cracks with no impact point, are covered in what causes windshield cracks.

How to warm or cool the car without thermal shock

The goal is to change the glass temperature gradually and evenly. These steps follow AAA, Mazda, Kia, Safelite and Pilkington guidance.

Pilkington’s frost bulletin ATS-161 states the principle behind every step: excessive temperature differences in glass must be avoided, “especially in winter”.

These habits protect intact glass and slow existing damage, but they cannot reverse a crack. Under the ROLAGS 002-2022 repair standard, a crack up to 14 inches (350 mm) can be repaired. A stress crack that starts at an edge with no impact point has to be replaced. Safelite says a crack that started at the edge is almost always a replacement job, whatever caused it. Safelite adds that a thermal crack that grew from a small chip may still be repairable.

Frequently asked questions

At what temperature can a windshield crack?

No automaker or glass maker publishes a single cracking temperature for windshields. What matters is the difference across the glass: Pilkington’s building-glass figures put the risk zone for untempered glass at roughly a 40 to 60 °F difference, and damage lowers that limit.

Can cold weather crack a windshield overnight?

An intact windshield rarely cracks overnight from cold alone. Safelite says water trapped in a chip can freeze, expand and turn a small chip into a long crack by morning.

Can a cracked windshield shatter in the cold?

A laminated windshield is designed to stay in one piece, so a crack usually grows longer instead of shattering. A crack should still be checked soon, because cold and defroster heat can extend it.

Why did my windshield crack without anything hitting it?

Many cracks with no visible impact start from a tiny chip or scratch that dealers find with a pen tip or a 10x magnifier, according to Infiniti’s bulletin. Thermal stress from defrosting or cooling then extends it.

Does insurance cover a windshield crack from cold or heat?

Safelite says comprehensive coverage typically treats thermal-stress damage like impact damage, and some states waive the glass deductible. Details by policy are in does insurance cover windshield replacement.

Sources

• Pilkington North America, Technical Bulletin ATS-123, Thermal Stress (2013-01-14) (checked 2026-10-26)
• Pilkington North America, Technical Bulletin ATS-161 (2013-01-14) (checked 2026-10-26)
• Viracon Tech Talk VTT-011, Thermal Stress Breakage (checked 2026-10-26)
• Infiniti Technical Bulletin ITB09-039K, Windshield Cracking (April 29, 2024)
• Subaru Service Bulletin 12-257-25R, windshield warranty extension (revised February 13, 2025)
• Mazda 2025 CX-5 owner’s manual, Winter Driving (checked 2026-10-26)
• Kia K4 2026 owner’s manual, Wipers and washers (checked 2026-10-26)
• AAA, How to deice your car’s windshield (checked 2026-10-26)
• Safelite, Does Cold Weather Make Windshield Cracks Worse? (April 2, 2026)
• Safelite, Why Do Windshields Crack in the Heat? (June 23, 2026)
• ANSI/AGSC/NWRD ROLAGS 002-2022, Repair of Laminated Automotive Glass Standard
• NHTSA complaint data files (received through October 22, 2026; CarGlassFix count by month of incident)