Snapdragons and even potted geraniums lived through winter. Warm winters provided impetus for experimenting with lots of marginally hardy plants, even tropicals. With so many variables in our maritime Pacific Northwest landscapes, the individual performance of plants will vary from garden to garden. Moderation of cold temperatures can be expected at lower elevations and near large bodies of water. More frigid temperatures always prevail on hills, and certainly toward the Cascade foothills and above.
Exposures also vary from the shelter of woods to a fully exposed bare hillside.
Plants don't experience the wind chill factor that affects warm-blooded creatures, but drying winds can cause water loss from plants. Some may be damaged by both freezing and dessication. Cloud cover helps to moderate the effect of freezing, because plants don't dry out quite as fast as they do in a long period of sunny days with frozen soil. Snow also moderates plant damage, acting as an insulating layer. In addition to the variables presented by the weather and the site of the plant, plants react according to their own genetic hardiness and their place of origin.