Cold weather may be a factor, since your battery loses a lot of capacity when it is cold. Meaning this issue could have been present for awhile, but was hidden until the weather got colder and stayed cold.
There's always a small percentage of defective parts, but the most common cause of this type of problem is the battery is being slowly drained by something in the electrical system. For example, aftermarket alarms, remote starters, stereos, trunk light staying on, etc.
Your electrical system just needs to be checked out. There's simple tests that can be done for the battery and alternator. If they are healthy, you probably have the problem with a hidden power drain.