Unless you just drove a car off the lot, it probably has a fair amount of cracks on it. Most of these cracks are very tiny, maybe even unnoticeable without a close observation or a keen eye.
The problem is that many cracks start out nearly invisible to the eye and slowly grow larger until they look like a frosted branch across your windshield. The good news is there's a lot you can do to slow this process before you have to replace the entire windshield.
Going Easy On The Defrost And A/C
In areas that experience winters and summers with extreme temperatures and conditions, cranking up the defrost/heat or the air conditioning is an invitation for the cracks in the windshield to grow. That's because, just like other materials, glass expands when the weather is warm and shrinks when the weather is cold.
These sudden temperature cause bursts of micro pressure on the molecules in the glass leading to added stress and expanding cracks. Instead of turning on the air conditioning immediately, it's a better idea to drive a minute to allow air to cool the windshield. After it's cooled, you can introduce cool air from the car. As for heating your car, it's better to start on at a lower temperature before turning it up to its highest point.
Of course, you could prevent some of this by...
Parking In Cool/Warm Areas
If you're one of the people fortunate enough to have a garage, especially one that's climate-controlled, then your car's windshield isn't at as much risk as cars parked outside. That is, if you actually park your car inside. But, even if you don't have a garage, a carport or other shaded areas works just as well.
In the summer and winter, the extreme shifts in temperature themselves are enough to cause damage to the structure of the windshield. The difference between a shaded area and direct sunlight is anywhere from 10 to 15 degrees. And that's just counting the direct heat outside.
In the summer, the glass of your vehicle acts like a greenhouse and traps the sun's energy inside. That extra heat from the inside stretches the glass even further, weakening the bonds and stretching the glass.
Just take caution when parking your car under a tree has heavy branches, small nuts, and fruits can drop and cause the cracks in the first place. And remember, if you're worried that the glass needs repairing, you can always take it to a professional at a place like Brite-View Glass for further advice.