Groundhog's Day is a great time to focus on any kids that may live in your apartment building or complex. Kids generally like animals and although it may seem like winter is never going to end, it is considered the beginning of the end for those adults who can't stand the colder weather. Maybe you want to set up a coloring station where kids can draw and color their own Punxsutawney Phil. Perhaps you can make or purchase cupcakes that have groundhogs on them and hide them in little cubbies for the kids (or adults) to find. There are dozens of things you can do if you want to get creative and it's always a bonus for the adults in your complex if the kids are distracted for a few hours so they can relax.
Valentine's Day is normally a more adult-centric holiday, but that doesn't mean it can't be fun as well! Maybe you could slide those little tin valentines that you used to hand out in schools under your resident's doors. A friend of mine always puts a couple of Hershey Kiss candies either on the cars of her residents or tapes them to their front doors with a little note. It doesn't have to be much, but just something so that your tenants know that you're thinking of them can go quite a long way.
It can be hard to see the warmth coming when you've been dealing with the past few months of cold weather, but February generally marks the last really cold month as long as we're lucky. There isn't much to celebrate in the way of normal holidays, but that doesn't mean we can't be happy! Try hosting some kind of small themed gathering and see if it goes over well enough to do it again next year!