Thermal cycling is the mechanism
Glass expands when it heats and contracts when it cools. A crack concentrates stress at its tip, so every expansion and contraction works that tip a little further.
Sacramento summers combine very high daytime highs with substantial overnight cooling — the classic inland valley diurnal swing. A windshield parked in the open goes well above air temperature in the afternoon and drops sharply after dark. That is a large cycle, every day, for months.
The air conditioning mistake
The worst single event is not the weather, it is what people do about it: getting into a car that has been baking, and putting the air conditioning on maximum aimed straight at the windshield.
That cools the inner surface fast while the outer surface stays scorching. The difference across the thickness of the glass, concentrated at a crack tip, is exactly the load that makes a chip run. If you have damage, cool the cabin with the windows down for the first minute and aim vents at your face, not at the glass.
What it means practically
A chip in Sacramento has a shorter window than the same chip in a mild coastal climate. "I will get to it eventually" is a strategy that works in San Francisco and fails here.
Tape it, park in shade where you can, and get it repaired inside a week. A thirty-minute resin repair is a fraction of the cost of the windshield it saves.
Need this done rather than explained? There is no shop to drive to. We come to wherever your car already is — your driveway, your workplace car park, an apartment lot, or the side of the road it stopped on — anywhere in greater Sacramento, with no call-out fee and no mileage charge. Give us the year, make and model and you will have a firm price before the call ends.