AFAIK it happened while i was parked. I was driving home (and I have 2 take two highways, one has trucks that I always try to avoid, the other doesn't) parked the car, don't remember any crack .... got in the car the next morning, and it had been raining. Lots of rain had flowed from the roof onto the hood, lots of rivulets.... I hit the wipers to clear them ... one doesn't move ... its the aforementioned crack. Wipers don't clear that ... Of course, I was pissed, but the rest of the story you know.