Here's the map of lightning over the last 24 hours. Thunderstorms in the Cascades on Saturday might have sparked off new fires but we don't have a handle on those yet. A red flag warning is in effect for the Cascades from now through 11PM on Monday, so fires will likely grow.
King, Pierce and Snohomish Counties
Winds will be driven by terrain, meaning smoke will likely drain into communities along the Cascade foothills and perhaps closer to some of the larger cities overnight. Light amounts of that Siberian/ BC smoke overhead may mix to the surface during the day, more so at higher elevations. Expect Moderate air at times, though pockets of USG cannot be ruled out. Air should be mostly Good further west of the Cascades.
Most of eastern WA
Siberian smoke continues to cause Moderate/ USG air in much of eastern WA, with fires along the BC border, the Chelan Hills fire and other smaller fires also contributing. This is likely to continue through Tuesday, with any new fires adding more smoke to the mix. Some areas of Unhealthy air are possible.
When will it clear?
A wind shift and cool down happens in western WA on Tuesday, commencing a slow removal of smoke. Eastern WA has to wait until Wednesday. Winds are expected to be strong during the transition, raising fire growth concerns even as smoke flushes out.