Well it seems like the coldest month in the western US should be February since it's closer to oceans than interior areas of the continent. This is called seasonal lag. It's a phenomenon where the shortest day of the year (Dec 21 in northern hemisphere) is NOT the coldest, which is mainly dependent on proximity to oceans. Interior areas typically are coldest in late December and early January while coastal areas are later. This doesn't seem to be the case for the west coast in the US. Why?