It gets seriously hot in Phoenix in the summertime, as in many days of afternoon temperatures well over 100 degrees Fahrenheit. The average highs from June through September top 100 degrees. Some people believe that when the temperatures get this high, your windshield could explode or blow out from your vehicle if you don't leave your windows cracked open. There is little empirical evidence to either support or refute this claim, but here are some thoughts on this urban legend.
In the past, windshields were made differently. In high temperatures, those windshields expanded beyond the capabilities of the frame of the windshield, and they could crack or blow out. Now, most windshields are made of laminated safety glass, which can expand and contract better within the frame of the vehicle.
When Cracks Happen
Be assured that in the summer in Phoenix, you won't see minefields of exploding windshields as you walk to your car in the mall parking lot. Chances are that if the windshield has cracked, it was damaged before the heat got to it. Auto Glass Services of Sacramento, California, explains on its website that if you already have a chip on your windshield, called a spider, it might crack in intense heat. If your windshield has no chips, it won't crack as a result of intense heat and sunlight, the usual Phoenix scene all summer long, Auto Glass Services says.
Auto Glass Services also says that if you have a small chip in your windshield and have been running the air conditioning set at a very cold temperature and then park the car in strong sunlight when the temperature is high, cracks can start from the chip.
How to Prevent Cracks
If you do have a small chip on your windshield, there are a few things you can do to protect it from cracking in the hot desert summer. You can invest in a dash cover, which will diminish the heat reflected onto your windshield. You can also get your windows tinted, which will reflect the heat away from the windshield. A common idea is to crack the window just a bit if you are in a safe neighborhood. You can also crack the sunroof if you have one. This allows air to circulate and somewhat reduces the chance of getting cracks in a windshield that is already chipped.
In any case, if your car will be out in triple-digit temperatures for a few hours, make sure you park in the right direction, pointed away from the sun, so the sun isn't beating down on your front windshield, which heats up the interior faster, and uses a window shade, if possible. They're cheap, and they make a big difference.
Even if you park in the shade, make sure that you don't leave your phone or tablet in the car in the summer and be especially careful not to leave children or pets in the car. And leaving full soda cans in the car is a big mistake you will regret if they explode from the heat inside the car. The car will be intensely hot, but your windshield should be OK.