Forecasters say cold, dry weather with areas of freezing fog will continue into the middle of next week in Washington.
The National Weather Service issued a fog advisory early Friday, warning visibility could be less than a half a mile in the dense fog.
"When it comes to when the fog and where the fog is going to burn off, it is almost the Magic 8 ball, the future is hazy, ask again later," says KING 5's Rich Marriott.
Marriott says the fog will diminish Friday afternoon, but similar conditions will return Saturday, Sunday and Monday.
An air stagnation advisory remains in effect through early next week. NWS says the stagnant conditions will allow pollutants like vehicle emissions and smoke to collect near the surface.
A curious part of the recent weather conditions is that it is actually warmer at higher elevations. While the lowlands are experiencing temperatures around the 30s, higher elevations are in the 40s and 50s. University of Washington Professor of Atmospheric Sciences Cliff Mass explains in his weather blog that such conditions are called an inversion, as it's the opposite of the norm.
The National Weather Service says a frontal system could arrive Tuesday night or Wednesday, returning rain to Western Washington and a chance of snow in Eastern Washington.
Marriott calls them "welcome showers" as they will clear out the air pollution.
A strong high pressure system over the Northwest is expected to last through the weekend, maintaining stagnant air conditions that could cause breathing problems for vulnerable people.
The Associated Press contributed to this report.