Cold cranking amps are rated at 0 degrees F. A few degrees below that is not likely to shift the curve much. However, batteries do decline in CCA performance pretty fast - in a warm climate, you might get 5-6 years from a battery, whereas the same battery would be “failed” - unable to start the car reliably - its second 0-degree winter.
Trickle charging is part of the solution in that keeping the battery full to the very brim with magical fire will help ensure it can crank the engine; charging also creates a little bit of heat, raising the battery’s core temperature and thus increasing the cold amperage. But an older battery at very low temps is going to struggle, especially with a large or high-compression engine.
In those cases, a block heater, a battery heater or both is the only solution other than a new battery every year. But trickle charging - battery tending - is a pretty miraculous thing for vehicles driven infrequently or needing every bit of juice to start.
(I just had to start a very temperamental vehicle with a very large engine - 7 liters, 10.5:1 compression, carbureted, no choke - after almost 3 months, in ~15 degree temps. With an aging battery. I almost got there. Had to throw my small charger on it in boost mode to get it over the hump and stay running. I hadn’t planned to start it until things warmed up, but a trickle charger would have helped immensely in this particular case.)