Always needs a jump to start

New battery put in about six months ago. It drove great since. Then had an issue with the brakes so car sat about two months. But was periodically started then it sat without being started about two to three weeks. Went to finally use it and would not start. No noise made just would not turn over. It did start when jumped but once you turn it off it will not start again unless you jump it. We did have a few extremely cold days and nights, so I wonder if that affected my battery because to me it just seems like the battery. But, I also know it could be a number of other things as well. So anyone have any ideas? Prior to me putting in a new battery the car did sit for a while probably about six to nine months.