How about museums that might be open during the winter, or the best waterfalls and light houses to see? Is the pictured rocks or sand dunes, vehicle accessible during the winter?
Many of the best waterfalls just become giant mounds of ice in the winter (winter is worst time if year for waterfall scenery). Also, due to unplowed roads a large number become inaccessible to anyone without a snowmobile or willing to strap on snowshoes.
Nearly all of Pictured Rocks National Lakeshore becomes inaccessible in winter for the same reason - unplowed roads.
I think most of the historical stuff in the Keweenaw closes down in the winter due to lack of visitors, but you'd have to check the individual places to make sure. I think places like the Calumet Visitor Center (highly recommended), Laurium Manor, and Calumet Theatre stay open in winter for tours.
Needless to say, if you aren't able / willing to venture out with some form of snowmobile, snowshoe, ski, snowboard, fat tire bike, etc, the U.P. becomes a much less scenic place in winter...
