this site has been indispensable during wild fires. but when watching air quality in my region, i’ve been finding myself more and more frustrated by a complete

this site has been indispensable during wild fires. but when watching air quality in my region, i’ve been finding myself more and more frustrated by a complete lack of explanation of what causes the plummeting air quality sometimes. during wildfires the reasons are obvious, but outside of wildfire season i have fairly regularly seen the air quality just plummet and we’re just completely left in the dark why its happening.