How high off the ground was yours? Mine was about 8 or 10 stories up, and because it was so huge, I saw it quite clearly.
I was trying to execute the 'end of the open interstate detour, but it was my impression that it arose from approximately 1000 yards away and ascended as it went over my choking-engine car. It seemed approximately two or three football fields in length and one in width; it filled my sunroof opening but not my windshield.