well they are all "summer cars" but in any of these states there is a risk of someone winter driving it. BUT new cars, especially cars the people treat nicely like bmw's, won't have one bit of a problem in the snow, in terms of rusting or whatever. MN has a decent selection, and if you found one at one of the dealers here (BMW Motorwerks Edina or Sears of Imported Autos) i would glady go check it out for you.
Welcome to BMWboard