I find it intersting that "Christmas Cactus" never seems to bloom at Christmas. My mother's poor plant is so confused that it blooms in February, some years. Hrm. I wonder if there are any cactus plants that wouldn't mind the snow much. Maybe there's an arctic cactus.
Good to see you have your survivors selected and relocated for the winter months!
There are 2 or 3 different cactus that are native to WI. I could not have been more shocked when I came up on a patch of prickly pear cactus in bloom in our Woods when we lived in Central Wisconsin. I think they grow as far north as Canada so you probably have some in some of the sandy areas of Minnesota also.
My 'Christmas' Cactus is random, too.