Fog, including freezing fog in some areas, played havoc with traffic Monday morning.
Several accidents were reported, centering on the Hockinson and Brush Prairie areas.
Meanwhile, the morning commute was very slow on the freeways. Between 8:30 and 9 a.m., for example, Interstate 5 was backed up to the Main Street exit in Clark County, forcing heavy traffic onto side streets.
The National Weather Service warned that drivers should be prepared for slick roads and the possibility of low visibility areas until the fog lifts.
Most flights at Portland International Airport were on time, according to the airport's website.
The Southwest Clean Air Agency's monitors show air quality has nudged into the "unhealthy" zone in Vancouver and was nearly as bad in Yacolt, where it was considered unhealthy for sensitive groups.
A Stage 1 burn ban is in effect, which prohibits outdoor burning and use of fireplaces and uncertified (usually older) wood stoves and fireplace inserts.
Tuesday should be more of the same: freezing fog before 10 a.m., with areas of fog until about 1 p.m.
Here's the National Weather Service forecast:
This afternoon: Sunny, with a high near 45. North northwest wind around 6 mph.
Tonight: Areas of fog after 10pm. Patchy freezing fog after 10pm. Otherwise, mostly cloudy, with a low around 29. North northwest wind around 5 mph.
Tuesday: Areas of fog before 1pm. Patchy freezing fog before 10am. Otherwise, partly sunny, with a high near 40. North wind around 5 mph becoming calm.
Tuesday Night: Areas of fog after 10pm. Otherwise, mostly cloudy, with a low around 35. Calm wind.