Read more. A good book can take at least a day.
Have a movie day, where you watch your favorite old ones or exciting new ones from morning til night.
Explore. Do the touristy stuff in your own neighborhood. It’s out in the snow, yeah, but it doesn’t have to center on the snow itself.
Take some classes – outside of school. Any enrichment courses around? Learn some conversational Spanish, or how to knit, or how to cook a three course dinner. Or whatever.
Clean out the basement. Or clean out my basement – that would take all week, here. :)
Spend the day with some other people, doing what they want to do. This works particularly well with older folks. Do you have nearby grandparents who never get to see you? I bet they’d love to.
Volunteer somewhere. There are all kinds of organizations in need, who don’t require an ongoing committment.