In colder weather, the charge is depleted from most batteries if not in service to a point that freezing of the battery is possible. The electrolyte in a battery basically turns to water if the battery is run down.
When a battery freezes the life of that battery is drastically shortened if the battery is not ruined at this point.

It's advisable that a battery tender is used on a battery in storage or a monthly charge is given using a small trickle charger not more than 10 amps with a tapering charge. Monitoring the battery temps when you use a trickle charger as not to overheat the battery.

Here's a chart that shows the freeze rate and temps of a battery.

http://i149.photobucket.com/albums/s45/bills985/Batteryfreezingpoints.jpg