On average, El Nino has brought wetter-than-average winters to northern California, but as these plots show, this signal seems to be most consistent for the strongest El Nino events. It's still too early to tell how strong this event will be. The temperature signal is pretty small, but there is a weak tendency for warmer-than-average conditions in northern California. If you would like to create your own plots of typical El Nino conditions over the USA or even over the globe, then this site is pretty useful.