Chill inside places with your friends. Play video games or board games. Text and call people ( like I do ). Or maybe just go outside anyway, sometimes when it's cold it's still fun to be outside just dress appropriately :)
It is the perfect time to stay with families and do something together. Maybe travel together is a good choice. Go hiking, go skating, play with the snow, go to the Ice sculpture Festival......or just travel in your own room is a fantastic experience.