In my case it is rare and seems to be related to relative atmospheric conditions. I am in a dry S. California climate. If the day to night temp goes from 70 to 50 (something like that), having the vents on fogs up every window very quickly and heavily and it can happen unexpectedly 5 minutes into a trip. There is a feeling of great humidity. Defrost or rolling down the windows take forever to clear them, but clicking on the a/c clears them up right away. Never noticed this on other makes either.