When the temperature drops your car will be harder to start. The engine will require more torque to crank over. The battery will have less current at given temperature, this is why you see two temperature points given for cranking capacity. Where the climate is severe (U.P. in Michigan and Barrow AK, for example) a battery blanket with heater AND engine block heater is required on chilly January mornings or the vehicle will not start!
If the oil gets cold enough, the oil can acutally become nearly solid! You don't even want to know what this would due to your engine!
Cheers!