You park your car at night with a small chip or short crack in your windshield—barely noticeable. By morning, it’s a long, jagged line stretching across the glass. Sound familiar? Windshield cracks can and often do spread overnight, especially in Ontario’s unpredictable weather conditions.
At RAM Auto Glass, we’ve seen countless customers wake up to a windshield that went from repairable to unfixable in just a few hours. Understanding why this happens can help you prevent further damage—and know when to act quickly.
1. Temperature Swings
Ontario is known for drastic overnight temperature drops, particularly in fall and winter. Glass naturally expands and contracts with heat and cold. When you park your car in a warm garage or after a drive and the outside air turns cold, the glass contracts—pulling on any weak points.
This shift in stress often causes minor cracks to lengthen suddenly. According to Environment Canada, freeze-thaw cycles are one of the leading causes of overnight crack spreading in vehicle glass.
2. Moisture and Ice
When water gets into a chip or crack and freezes overnight, it expands. This expansion pushes the glass apart, turning a chip into a spiderweb crack almost instantly. Even condensation or light rain can seep into the crack before the freeze begins.
This is one of the reasons why we don’t recommend waiting to repair even the smallest chips—especially in colder months.
3. Internal Cabin Pressure
Closing your doors with the windows up creates cabin pressure that can flex the glass. Overnight, when the adhesive and rubber seals are stiffer due to cold, this added pressure from simply opening and closing doors can worsen a crack.
It’s a good idea to leave your window slightly cracked open if you’re dealing with an existing chip and want to prevent pressure buildup overnight—especially in enclosed garages.
4. Previous Damage Weakens the Glass
Even if your windshield crack appears stable, it weakens the structure of the glass. Vibration, shifting temperatures, and structural tension from the car’s frame can all put strain on that weak point. Overnight, these forces continue to act on the glass—even while the car is parked.
In many cases, the crack has already started spreading microscopically, and the stress of night conditions simply finishes the job.
5. Improper DIY Repairs or Delayed Professional Fixes
DIY repair kits may not fully seal the crack, leaving moisture or air inside. If a chip isn’t filled properly—or at all—it remains vulnerable. Overnight temperature drops amplify the issue.
At RAM Auto Glass, we use professional-grade resin and UV curing tools to ensure a permanent bond that can withstand Ontario’s harshest nights. Our customers trust us because we help prevent further damage before it starts.
Can I Prevent Overnight Spreading?
- Repair chips immediately—especially before temperature drops or long drives.
- Park indoors or under shelter when possible.
- Cover the windshield with a frost guard or protective layer overnight.
- Leave windows slightly open to reduce pressure buildup inside the car.
- Avoid blasting defrosters onto cold glass first thing in the morning.
What to Do If You Wake Up to a Larger Crack
If the crack has grown overnight, don’t panic—but don’t ignore it either. Call RAM Auto Glass for a free mobile assessment. If it’s still repairable, we’ll fix it on-site. If not, we’ll offer a fast, affordable replacement—often covered by your insurance.
Related Reading
- How Weather Affects Auto Glass Cracks in Ontario
- How to Prevent Windshield Cracks From Spreading
- Does a Small Windshield Chip Always Require Repair?
Book a Mobile Windshield Repair Before It Gets Worse
Don’t let a chip turn into a costly replacement overnight. RAM Auto Glass offers mobile chip and crack repair across Vaughan, Toronto, Markham, and nearby areas. We come to you, even in cold weather.
Call us now or book online at (647) 777-7080 and fix your glass before the next temperature drop does it for you.