You could try, when you're not home, leaving several damp towels around the edges of the windows and at the base of the door. Basically anywhere that air comes into your apartment.

The advice from sktarq is more permanent, but insulating your whole apartment might be costly (and probably isn't your job since you're a renter) and masking tape can harm the paint. So I'd suggest trying just some towels and see if that helps. If that solves the problem, you can look into something more permanent.