Connie and I went out to dinner last night with some friends and while we were in the restaurant the C5Z got rained on. Storm was over when we came out, but obviously I had water on the car. Just drove on home and let the wind blow off the water.
There was some water spotting when I looked at it today, but just used some Flash detail spray and they came right off.
Probably worst case is to get a rain shower and then have the sun pop out, with your car sitting in direct sunlight. Not only will the evaporating water leave residue rings, but the water itself can act as a bit of a magnifying lens and actually etch into the clear coat from the concentrated rays from the sun. At least that is what I have heard, and it sounds plausible....