I believe there was a huge blizzard that hit most of the state the week before the semis in 93 or 94 that forced all of the eastern teams to play in the Dome and all the western teams played in the DakotaDome in Vermillion.
That was the impetus to move the semifinals indoors.
That was the year that Halloween in NW got cancelled. I want to say it was either 90 or 91. My father in law and I were just talking about this tailgating at the Texas game and he thought I was crazy when I said that USD hosted some Iowa playoff games.