When I lived in Phoenix I was always careful not to wash the windshield when
it had been sitting in the sun, although it's okay to do it when it had just
been driven because the air flow cools the glass, even if only to 115F.
When we moved to Flagstaff I stopped worrying about it. Big mistake. I
washed our Prius when it had been sitting facing the sun and the windshield
cracked. D'oh! The upshot seems to be if there are no pits or nascent cracks
you may well get away with it. Unfortunately, windshields pit in the first
week of service around here.