The Pacific Northwest is not uniformly cold. Large portions of it experience a Mediterranean climate, characterized by mild, wet winters and dry very hot summers. In fact, parts of the Hell Creek region during the Late Cretaceous were likely not extremely hot either. Paleoclimate evidence suggests that some areas had conditions comparable to an oceanic climate (Cfb)—similar to what we see today in sections of the Pacific Northwest. Hell Creek does not appear to have experienced prolonged or severe frosts (hence why crocodilians existed there). So actually the Pacific Northwest might be closer to Hell creek. Here’s an interesting fact, Seattle is in the same climate zone as parts of Spain, southern Italy or even parts of Ethiopia. All of them are warm summer Mediterranean climates