Kathy said,
You should stay along the I5 corridor. Don't consider staying on the coast during the winter. Very cold. Very damp. Very windy - they can get high winds on the coast but here along I-5, it's buffered by the range of coastal mountains between I5 and the coast.
Stay away from cg's on the rivers. Rivers flood in the winter with all the rain. Don't park under big trees either... pine needles are not fun when tracked into the rig all winter long.
We go to the coast in the winter and will be going next week and in Feb. you just need to camp at the right places and travel in between storms. Sometimes the weather is better on the coast than inland, the south coast is nicer than the northern end .We have been doing this for years.