Driving up State Route 18 from Maple Valley, my rear view mirrors suddenly fogged over. There was no fog outside-why did that happen?
Let me tackle this question by mentioning when I flew, I occasionally encountered a condition called 'splat icing'. That's caused by a cold aircraft flying into moisture-laden air...that then freezes on contact with the airplane. In the case mentioned, I believe the driver moved from cold air into somewhat warmer, more moist air...which may not have cooled enough to form ice on the car, but did rapidly condense into fog. There may not have been enough moist air to form widespread fog...but the very cold car was enough to 'do the trick'.