I spent a decade in Michigan one winter, so I feel for you.
If you can't ride, then walk. If you're so inclined, you could take up jogging. Might need slightly more special-purpose gear for running. You can use running gear to walk, but walking can also be done in your normal winter clothes, if you HAVE good outdoor winter clothes.*
There are people who ride year-round. It takes an investment in winter riding gear. Not just clothes, but where you are, a winter beater bike might make a lot of sense - same principles as a winter beater car.
* - A lot of people go for years without decent winter clothes, even living in places like Michigan, simply because their only experience with the outdoors involves getting from one heated box (car or building) to another.