Tips on Avoiding Cracked Windshields
When a stone chips your windshield, have it repaired ASAP. Until the damage is repaired:
In Cold Weather
Keep hot air and hot water off the windshield. Avoid hot air from the defrosters if possible. Don't run your car through a car wash that uses hot water.
In Hot Weather
Avoid cold water on hot windshields. Wash your car mornings or evenings when it's coolest; not mid-day.
After your windshield is repaired, these restrictions no longer apply.
HOWEVER, the above conditions can aggravate stress points in your windshield and result in stress cracks, even without the obvious presence of stone chips and short cracks.