This fog moved in very quickly. It might have only taken 5 or 10 minutes before going from blue sky to this. In the next few minutes it wasn't worth trying to take a picture as it was a white-out. This was a very thick fog, moving in and darkening everything like rain clouds. Very typical for this part of the mid-west....warm days, wet ground from some recent rains and cooler nights. Speaking of cooler nights....the 30's are in the forecast form weekend after next.