Check the oil type, in cold weather sometimes the oil becomes thick and gloopy and the engine will turn as if going to start but wont bite.
Otherwise try the battery making sure it has a high enough charge and that the connectors are ok.
If neither of them then there may be water i the fuel. Contamination means that the water might freeze in the pipes.
Only way round this is to get the motor somewhere warmer.
Annie
December 2007