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Why Does Window Glass CrackMost of us have been there: You go out to your car to head to work in the morning and discover a large crack in the windshield. You’re certain it wasn’t there yesterday, so where did it come from? It may seem like it simply happened for no reason at all, but there was likely an underlying reason hidden from view.

Of course, there are some obvious things that could cause auto glass to crack. Rocks or gravel flying up from the road while you’re driving or a large storm that causes downed tree branches (or even trees!) to fall on the vehicle are good examples. However, if any of these were responsible for your cracked window, you would likely have known about it immediately. When glass develops a crack seemingly out of nowhere, it’s far more likely that it was caused by something unseen.

Changes in Temperature

Environmental changes cause glass to expand and contract, placing windows under stress. Because glass expands and contracts quickly along the edges, it creates pressure at the center that can lead to a crack. 

Stress cracks can be caused by sudden temperature changes, which are fairly common in Fort Worth, Texas. Even though the weather is fairly mild year-round, chilly mornings are often followed by afternoons with significantly warmer temperatures. It’s not at all uncommon to see a difference of 30 degrees between the low and high temperatures on any given day.

Your vehicle’s defroster can have a similar effect by rapidly heating a frosted-over windshield. Instead of turning the defrost up to high when you get in the car, start slowly and gradually turn it up. 


The sun has a similar effect on auto glass as temperature changes. Because window glass heats up faster around the edges, it expands faster around the perimeter than it does in the center. The direct heat of sunlight speeds that process up, which may explain why perpetually sunny Arizona and Florida lead the nation in auto glass insurance claims. The stress of the rapid expansions and contractions results in cracks. 

Pressure Changes

Much like how temperature changes and sunlight can place stress on auto glass, so too can changes in pressure. Temperature and weather can have a direct impact on environmental pressure, causing increased humidity or other changes in the air. Other factors that could change pressure are high-speed wind gusts and fast driving over an extended period of time.


Hail storms, which may or may not be accompanied by rain, are frequent in the Dallas-Fort Worth metro area. In fact, north Texas has been dubbed “Hail Alley” because it gets hail more often than most of the country. Texas as a whole consistently leads the nation in auto glass claims for hail-related damage, most of the time by a long shot. 

While it may seem obvious that large pieces of hail can crack a windshield immediately, smaller hailstones can cause damage also. A single small piece of hail may not directly cause glass to crack, but the stress of frequent small hailstones hitting the windows over time certainly can. 

How to Prevent Auto Glass From Cracking

Some cracks in your vehicle’s glass are unavoidable, such as those caused by falling debris or gravel kicked up by other vehicles. However, you can prevent some cracks by taking preventive measures.

Keep your vehicle parked in a garage or under a carport whenever possible. If neither of those is an option, at the very least park in the shade. If there are any weak spots in your windshield, a single hot, sunny day can cause a crack to develop. Similarly, parking in a shaded area can prevent existing chips or cracks from expanding any further.

It’s important to note that even a very small crack will not simply go away. Quite the opposite. It will continue to expand gradually until it’s fixed. In some cases, even cracked auto glass can be repaired. However, more often than not, if the crack is larger than 1 inch long, the glass will need to be replaced. A windshield may also need to be replaced entirely if there’s a crack that’s situated directly in the driver’s line of vision, no matter how small.

Whatever your auto glass needs are, Advanced Auto Glass has you covered. We have two convenient locations in Weatherford and Fort Worth, Texas, along with convenient mobile service. Also, all our glass installations come with a warranty. Our professional technicians are experienced in handling a wide range of auto glass repairs and replacements, as well as residential and commercial glass needs. Our biggest priority is getting you back on the road quickly and safely, so contact us today! Se habla Español!

Call Us At (817) 595-3200