How long have you lived in Cali... at all? Seriously. Sacremento is a breeze in the winter. If some rain means you need new tires... do it. I live in the high desert... never have I swapped tires for a winter season... and we get the usual sun... but also in the winter rain and some snow. Don't drive like a **************** stick and you should be fine.
Unless,meh, global warming.
You've a year? Save your money... wait a year... move... and then scope out the local weather specs.