Hi and welcome to the Forum.
'Cold-cranking amps (CCA) measure the battery's ability to start your car even on an extremely cold weather. During freezing condition, your car will be hard to start (or to ignite) because the car's engine oil thickens and chemical reactions, in turn, slow down. The cold-cranking amps also refer to the number of amps a battery will be able to support for 30 seconds at 0 degree temperature (until battery voltage reaches below minimum level). Choosing a battery with a high number of CCA is better; particularly to those vehicles being driven in a cold climate. A higher cold- cramping amps assure that your car's engine will start obediently even on snowy mornings'
http://hubpages.com/hub/Choosing-a-Car-Battery---Guide
Hope this helps.
