PORTLAND, Ore. – A cold and foggy start is expected across northwest Oregon and southwest Washington late Wednesday night into Thursday morning, as temperatures dip into the mid-30s and dense fog reduces visibility along major roadways.
According to the National Weather Service in Portland, overnight lows will fall between 34 and 38 degrees in lower elevations and rural valleys, creating a 15–25% chance for patchy frost. Sensitive plants and outdoor plumbing could be affected in outlying areas such as Hillsboro, McMinnville, and Salem.
At the same time, dense fog will form along the I-5 corridor from Portland south to Eugene, and north through Longview, Washington. Visibilities may fall below a quarter mile in spots, with locally lower readings possible through early Thursday. Morning commuters should expect slow travel, fog delays, and limited visibility for bicyclists and pedestrians.
Forecasters urge drivers to use low-beam headlights, allow extra stopping distance, and reduce speed in fog-prone valleys. Conditions should improve by midmorning Thursday as the fog lifts, leaving partly sunny skies and highs in the upper 50s.
Cool, dry weather will continue into the weekend, with chilly nights and light morning fog expected through early next week.
