The National Weather Service in Seattle has issued a frost advisory for Saturday morning. The advisory is in effect from 4am to 9am.
The coldest low temperatures of the early fall season are expected across the western Washington lowlands this weekend. The unseasonably cold minimum temperatures will be the result of a cold air mass that moved over the region from the Gulf of Alaska on Friday.
Saturday morning minimum temperatures are likely to be in the the 30s with upper 20s in outlying areas and over the southwest interior. Current forecast lows are just a couple of degrees above the records. The first frost of the season is expected in many locations.
A frost advisory means that frost is possible. Sensitive outdoor plants may be killed if left uncovered.