Is it possible for me to check books out over winter break?

Yes! If the library is open, you can check out books over break.

If the due date falls on a day when you are not in St. Mary's to return them, you can always renew your books online: http://catalog.umd.edu/patron=go

And you can always return your books to the book drop in the library building lobby, which is open even when the library is closed!