9 Reasons Why Windshields Crack Overnight?

Windshield Cracked Overnight

Windshields are made of glass. As it happens, glass is one of the most rigid materials there are. Glass can take a lot of force before breaking, but it becomes incredibly sharp and dangerous when it does break, leading to the need for windshield repair. A windshield can break for several reasons. The most obvious is that they can get hit by a hard object like a rock when you’re travelling at high speeds. But, sometimes windshield cracks are more mysterious, appearing in the middle of the night when your car has been safely sitting in your driveway.

How is that possible? Continue reading to find out!

Reasons Why Windshields Crack Overnight

Water Expansion

Water is made of molecules that are constantly in motion, and it will naturally seek an area of the lowest resistance. When water freezes, its molecules expand – making up to 9% more space than the liquid. This expansion can put significant pressure on an object, including windshields. The same phenomenon occurs with ice cubes expanding in a freezer or liquids expanding as they freeze (think about what happens when you leave too many ice cubes in the freezer). A hairline crack forms on the glass where it’s weakest, at weld points or around poorly bonded sealant. If this crack allows enough water to enter the vehicle’s interior, it could cause more damage during freezing temperatures.

Vehicle in a Cold Garage

Parking your vehicle in an unheated garage or outside during the winter months could lead to cracking. A warm body heats the car’s interior, while cold air outside can contract and cause enough pressure inside to break the glass. If you must park in a non-heated garage, make sure to use a dark curtain or similar item to cover the windshield at night. This will help keep out some of that cold air during temperature drops.

Insects Attracted to Interior Lights

Insects, such as moths or gnats, are attracted to light and often fly directly into the interior of a vehicle when they see it. Sometimes, they collide with large surfaces like windshields at high speeds – causing enough damage for cracks to appear. Always be aware that insects can strike just about anywhere on a car’s exterior, including the corner of the windshield, but especially in its direct line of travel. If you park your vehicle near where insects congregate (near a fence or tree line), keep an eye out for any signs of impact on your glass and give it a good wash before taking off on your next trip!

A Small Hairline Crack

Small hairline cracks in the glass are relatively common and can be caused by many things – usually an object that strikes the windshield. If the damage is minimal, it often cannot be felt when driving or looking out of the vehicle. A sure sign that it’s there arises when you attempt to defrost your windshield – moisture collects around this crack, distorting your view. While these cracks should not be driven long-term, they are not always a safety concern themselves. Replacing only the damaged glass will do the trick in most cases!

Meteorite Strike

A direct impact from a meteorite might seem like something out of science fiction, but it has happened before! In 2013, a meteorite struck a woman’s car in Russia and caused significant damage to both the paint and glass. The chances of this happening are rare – there have been approximately 200 documented cases of cars being hit by objects from outer space – but it does highlight how fragile windshields can be. Although a direct impact from a space rock might be hard for some people to swallow, even something as small as a pebble at high speeds could lead to cracks or shattering while driving.

Incorrectly Installed Windshield

A correctly installed windshield is very strong – capable of withstanding three times the pressure that an untreated piece of safety glass could withstand. Unfortunately, that doesn’t mean that they are invincible. A poor installation can be caused by cracking during the original process, but it’s more likely to occur after an impact or due to the age of sealing materials. You might even experience some cracks if your vehicle is driven on a poorly maintained road! Always have your windshield checked and thoroughly inspected for any damage, and make sure you get a clean installation when you replace it. The last thing you need is an improperly installed windshield, which could cause all kinds of issues for your safety!

Age and Wear and Tear

The age of your vehicle and wear and tear from exposure to elements like sunlight is likely to weaken your windshield over time. As it gets older, the adhesive is more prone to breaking down, and the glass itself will eventually succumb to decades of use (and abuse). That said, even brand new windshields aren’t entirely safe as you drive down the road! The materials used in their construction can still become damaged through careless driving or even normal wear and tear.

Poor Weather Conditions

As a windshield is exposed to the elements, including wind, rain, snow, hail, and more, it might experience some damage from time to time. It can be caused by sharp objects that have been kicked up from the road or even through something as simple as a gust of wind that catches your car just right. In addition to external factors like weather conditions around you, your windshield has its internal stresses going on at any given moment – even when parked at home in the middle of the night. The pressure between two surfaces often causes cracks if the glass is too thin or due to further damage. The material used in car windows helps them withstand a lot of this stress (so make sure your replacement includes these advanced materials), but it isn’t impervious to damage.

Glass Impurities inside the Windshield

Impurities like silicates, air bubbles, and dirt get trapped between layers of glass when installed together with the adhesive. These objects act like stress points on your windshield, which cause invisible cracks over time. When these cracks grow in size after an extended period, they become flaws that look similar to spiderwebs under the surface of the glass.


In the end, there are a lot of factors that play into why windshields can crack overnight, including ageing, environmental conditions, and even how it was manufactured. It’s essential to get your vehicle’s windshield repair as soon as you find any damage to avoid more extensive and costly repairs in the future.

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