Heat and Windshield Breakage

By Penny Stacey

Hot weather windshield
The nice weather of summer can be great for barbecues, pool parties and more, but it can be hard on your windshield. Your windshield is more likely to crack—and cracks are more likely to spread—when the temperature changes. Temperature changes cause glass to expand and contract, which can make your windshield a bit more fragile. Likewise, many of us are on the road more in the summer as we travel on vacations, to visit family or just make runs to the local pool. All of this leads to an increase in broken windshields that will need to be replaced.

Hot Temperatures Stress Windshields

Temperatures swings can put extra stress on the windshield and make it more prone to breaks. Likewise, if the glass cools too quickly this also can cause stress on the windshield. Experts recommend that you take your time in cooling your vehicle’s interior (and therefore the glass) so that cracks are less likely to expand. This might mean turning on your air conditioner to low at first, instead of going full-steam at once when you turn on your car. Also, many say you should be careful about slamming your doors too hard, as even this type of jarring can lead to increased stress on the glass.

More Travel Means More Broken Windshields

While the sun may stress your windshield, summer time is often a time for people to de-stress themselves. More vacations mean more road travel, and more road travel means more broken windshields. Last August, U.S. road travel was up 3.4 percent over the previous year—with a total of nearly 285 billion miles driven by vehicles in the United States. So as you plan your summer road trips, keep in mind that anytime you are on the road, the probability of a broken windshield increases. Combine this with the above stress issue, and you have a recipe for a rising number of broken windshields.

Watch Your Windshield for Damage

You can’t control the temperature, so what should you do? First, keep a close watch on your windshield. Inspect it often. If you get a crack or a chip in your windshield, the hot temperatures can cause the chip or crack to expand more quickly.

As soon as you see a chip or crack appear in the summer, you will want to get it fixed. If you do so quickly enough, it can sometimes be repaired (without having to have the entire windshield replaced). In a repair, a special kind of resin is injected into the break to keep the crack or chip from spreading. The crack or chip likely will still be visible after repaired, but this will at least save your windshield—which is good for both the environment and your pocketbook.

However, if the crack or chip expands beyond the point of repair, the entire windshield will need to be replaced. This is why it’s important to watch the windshield closely and ensure that you are aware of any chips or cracks as soon as they appear, and contact an auto glass shop quickly to check out the damage.

Be Cautious

If the windshield does break beyond repair, you will want to account for this when it is replaced. Many urethanes (the substance used to bond a windshield to the vehicle) can only be used under certain temperatures and humidity conditions. You will want to ask the technician doing the work if the urethane being used is appropriate for the hot weather, or find out if there is an indoor location at which the work can be completed.

Additionally, you’ll want to pay attention to the Safe Drive Away Time (SDAT) (also known as Minimum Drive Away Time or MDAT)—the time that your vehicle needs to allow the adhesive to cure before it can be driven after a windshield replacement. The MDAT can vary depending on the outside humidity and temperature, and your technician should provide details about this to you. (Conversely, if you are getting your windshield replaced on an extremely cold day, this can affect the SDAT as well. Any extreme temperatures, hot or cold, need to be accounted for—and you should ask your technician for details on the type of urethane that is used.)

The company you choose to replace your windshield may even ask you to come into the shop or your garage can be used so that the work can be completed indoors (and at an appropriate temperature). If an indoor bay, garage or shop isn’t available, the shop may simply suggest you wait another day or two, until the weather conditions change.

What Now?

If you do find yourself in need of a summer windshield repair or replacement (or anytime for that matter), there are many quality auto glass businesses out there available to replace your windshield. Check out the Glass.com auto glass service locator today to find a shop to replace your windshield. Glass.com has affiliate shops all over the United States ready to replace your glass when needed. We let you compare instant price quotes from the hops in your area and book with the shop that’s right for you. You will want to make sure you get the best deal, to allow you more money for those summer vacations.

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14 responses to “Heat and Windshield Breakage”

  1. I’ve got an older car and the windshield recently cracked without any sudden impact. I think the biggest cause of it cracking was the heat and the fact that it’s about 40 years old. It’s a rather curious situation and I’ve never had it happen before, so, doing as you recommend and contacting a professional about what to do could be helpful because finding out whether I should replace it so it doesn’t happen again or just repair it would be good to know.

    • Hi James, there could be several reasons why this is happening, or a combination thereof. First, inspect the glass thoroughly before removal to ensure there is no pre-existing damage. Second, if the glass gas been sitting in direct sunlight, it might be best to move it to shade before removal to let it come down to a moderate temperature prior to handling. Third, ensure that the removal process is being performed correctly with the proper tools. Lastly, be sure the glass is being stored properly in a windshield rack.

  2. Does a windshield need to be warmed up slowly from 10 degrees before a chip can be repaired or should it be done cold?

    • Hi Kadyn,

      Windshield repair technicians may use different tools, techniques and resins to fill chips so the answer to this question may vary depending on the tech’s experience level and the equipment they use.

  3. I have a Mazda CX5 still under warrenty. The other morning I wet out to drive the vhicle and there was a crack in the windsreen. The vehicle is parked under my house in a secure estate so it would not have been vandalised. It was particularly hot the previous day in the carport. Could the heat have done it? I reported this incident to Mazda Technical and the dealer but typically they are both trying to sidestep the issue.

    • Hi Tom,

      Yes- it is possible that the heat may have caused the crack to occur “spontaneously”. Look at the damage closely and see if there is any place that looks like it could have been impacted by an object. If so, it wouldn’t be considered a “spontaneous” break. It’s possible that there was a very small impact at some point that went undetected, but spread due to the temperature.

  4. I have a question. I just bought a 2017 F150 and within 2 weeks a rock hit my WS. Within 12 minutes it traveled the length of the WS & had to be replaced. After 3 months of owning it, I got 2 more rock chips and repaired them. Then after 5 months, another chip happened and when I went to repair it, it cracked the full length. Now I’m getting a 2nd windshield installed in only 6 months of owning this truck. There has got to be something going on with auto glass quality? I’ve driven trucks since the 70’s and lived in TX. and never had this much grief. I’m really sick of it and even my insurance company is getting alarmed at 2 windshields and multiply repairs within 6 months. What the heck is going on with auto glass? Thanks.

    • Hi Joy,

      I can certainly appreciate your frustration! To start, when you had the first windshield replaced, was it replaced with an OEM quality windshield? Replacing with an aftermarket windshield could raise questions of quality. Second, have you noticed more road work on the roads you’re travelling? More inclamate weather, or anything else that could cause more debris on the road? Even extreme fluctuating temperatures could have an effect on windshields. Lastly, I would say that if you haven’t had to replace a windshield since the 70’s then, statistically, things are catching up with you since the average driver replaces a windshield every 8 years.
      Hopefully this is the end of your streak for a while!

  5. Penny, thanks for your comment about how you should replace your windshield when the crack spreads. I like how you said that you should always hire a professional to do make any repairs or replacements. My husband and I are looking into getting our car’s windshield replaced because it has a large crack in it.

  6. Can heat cause the windshield to become brittle? I have a COVERCRAFT UVS100 Custom Sunscreen that’s made specifically for my car. It has Triple Laminate Construction and a Foam core center that acts as an insulator. I noticed that the side facing the windshield gets very hot here in Houston, TX. Could this heat harm the windshield? Should I not use this sunscreen on my 2017 Infiniti Q60?

    • Hi Mark,

      This is a great question! Glass is a very unique material in that is is really neither a liquid nor a solid because it exhibits characteristics of each state. There is no exact freezing or melting point. In a cooled state, molecules do not move. They are randomly configured, but they will not crystallize. In a warmed state, molecules will move about freely. The higher the temperature, the greater the movement.

      So your windshield actually becomes less brittle as it heats up. In theory, if it become hot enough (HIGHLY unlikely) it would sag and cave in rather than break. What you need to be cautious of are temperature differences which cause rapid heating or cooling. Let’s say that the sunscreen causes your windshield to heat up to 120 degrees when the outside air temperature is 20 degrees. This could be cause for concern. Or if you immediately blasted your air conditioning on defrost mode after using the sunscreen in the summer time.

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