For the most part, air quality in much of Washington, except areas near the eastern foothills of the Cascades, has returned to "good" levels.
However, most residents will experience stagnant air with partial daytime clearing over the next two days. Stagnant air can lead to dangerous conditions.
Strong temperature inversions coupled with light and variable winds will mean the air and any smoke that is present will not be dispersed well or quickly for now, according to Dr. Ranil Dhammapala, a forecaster for the Washington Department of Ecology.
Smoke from Eastern Washington wildfires will continue to affect communities near the fires over the next several days. Some light, southwesterly winds will develop today, Sept. 18, but they may not be strong enough to blow air pollution away. Some communities in the northeastern part of the state might experience periods of smoke.
The National Weather Service has issued a stagnant weather advisory to last through at least 5 p.m. this coming Wednesday for the following areas: Lewiston/Clarkston, lower Garfield and Asotin counties, the Wenatchee area, the Waterville Plateau, and the Kittitas and Yakima valleys. This includes the cities of Lewiston, Clarkston, Wenatchee, Chelan, Entiat, Cashmere, Waterville, Mansfield, Ellensburg, Thorp, Naches, Sunnyside, Toppenish and Yakima.
The worst air quality will be in the late night and morning hours because the smoke gets trapped near the ground during morning temperature inversions.
In some areas the air inversion and stagnant air will lead to hazardous air quality that could lead to aggravated respiratory problems, illness and even death for sensitive people.
Conditions will vary all over the state over the next few days depending on wildfires, wind and terrain. When smoke hangs in the air, residents are advised to take common sense health precautions, consider advisories and alerts from their local health departments and consult with their personal physicians. Schools and athletic directors should consult with their local health authorities or medical personnel to determine when to curtail outdoor activities.