2002 Nissan Maxima

It was time replace my battery. I have been through 3 batteries in the past 2 months. After a
cold night, its as if something is draining the batteries.
Some mornings I have gone out to a completely dead battery that can not be jumped. I've been told everything from the battery has a bad cell to the fact that the hood has snow on. This morning I awoke to a dead batter again, however it was able to be jumped. I also have recently noticed a slight clicking sound from the inside of the car, that seems to be coming from the fuse area under the hood even when the car is turned off. This morning I ran it by a local mechanic how said it might be the clock that sits in the center of the dash. I don't believe this is the case since I never noticed it before. Could the clicking be related to whatever is draining the battery? And if so, what is the cause? Thank you