Udo, I think Tori means with Cali's Lampropeltis getula californiae... Correct me if I'm wrong.

To answer your question... It is not always clear what triggers some snake species to start mating late in the season. You call it breeding, but copulating does not neccesary mean that the female actually gets fertilized.
There seem to be species where the female stores the sperm untill it is spring again. This is mostly in regions where the winter is long and the active period for reptiles is short. So in this way they do not have to wait for a male in spring.