In the rest of the country the weather is dominated by fronts and the interplay of different air masses. California’s weather is also dominated by frontal activity during the winter. Whether the skies are clear (or raining) depends on how various fronts pass relative to our location.
In many cases a front will pass and the weather will still be marginal. Maritime air masses tend to bring unstable air. Thus even though a front has past our skies are still filled with clouds and unstable skies.
Our best cases in winter our when the continental air masses control the skies. These tend to be drier (but in the case of the cP also bitterly cold).