All I ever needed in the winter around Seattle was a Wind proof vest over a jacket and thick head band leaving the top open for vapor. But now that I can't use my legs, and depend on a motor I had to get a wind proof Balaclava, a fur cap and insulated vest over my wind resistant jacket. It all depends on how much heat you generate with your muscles. I know some people are such wimps that they cannot even rife in the rain no matter how warm it is. Yet it is easy to wear a rain coat w/rain pants and water resistant cap-n-gloves. How ever it is easier to to not be drenched in sweat with an electric bike [which is easy to rain proof with silicon].
Rain capes are essential for the pacific north west.