Dozens of wildfires burning across the Pacific Northwest and Canada are decreasing air quality throughout North Idaho — and it’s uncertain when skies will clear.  

Air quality advisories are in place in many southern Idaho counties, and officials say the Air Quality Index across North Idaho is likely to reach advisory levels as wildfire smoke continues to drift into the area. Dan Smith, the regional airshed coordinator at the Idaho Department of Air Quality, said people can expect “real increases” in AQI in the coming days and even weeks, depending on several factors.  

“Wildfire locations, thermal inversions and our relatively narrow mountain valleys all contribute to local air quality,” Smith said. “Right now, we are being impacted by the fires in Oregon, Lewiston, and Yakima. British Columbia smoke is heading south into Montana and is affecting much of the Midwest. I see these trends likely continuing as the summer progresses.” 

Because of the cold, dry front that arrived Wednesday night, thermal inversion is “pushing” the smoke into lower elevations, which is why people across the region can see, smell and even taste the smoky air. Thermal inversion is a weather phenomenon that involves warm air sitting atop cooler air in the atmosphere. Typically, the opposite is true. 

Communities situated in valleys could see especially smoky conditions in the coming days as smoke settles between the surrounding mountains. 

It is estimated that up to 90% of the smoke impacting North Idaho air quality is coming from Oregon’s Durkee Fire, which is currently the largest active wildfire in the U.S. at over 300,000 acres.  

Local AQI is expected to remain in the moderate range for the next several days. While moderate-range air quality is acceptable, those who are especially sensitive to air pollution may want to take extra precautions.