EUGENE, Ore. - Smoke from a wildfire in Central Oregon crept back into the Willamette Valley on Monday, slowly but surely driving air quality numbers to their unhealthiest level since the fire started.
Air quality monitors in downtown Springfield, south Eugene and Cottage Grove were recording air quality in the good range on Monday morning, but smoke from the fire was visible in the air and at higher elevations.
The smoke settled as the morning went on, with the air quality pushing into the moderate range by 10 a.m.
By 11 a.m., monitors were recording the worst air quality in a month.
And by the noon hour, air quality had hit the unhealthy range. People with breathing problems should avoid the smokey air.
"After a strong onshore flow kept the area clear of smoke over the weekend, winds shifted overnight, pushing smoke over to the west side of the Cascades," said Sally Markos, spokesperson for the Lane Regional Air Protection Agency (LRAPA).
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The Pole Creek fire near Sisters has burned across 16,500 acres.
Some of the smoke comes from the wildfire's active burning; other smoke comes from "burnout" activities by firefighters, where crews use fire to intentionally burn fuels and create a containtment barrier around the wildfire.
The National Weather Service is forecasting southwest winds for Tuesday, which should clear the smoke out of the valley.
Central Oregon and Washington - where a massive complex of fires is burning - face inversions trapping smoke in valleys like a lid on a pot.
Northwest residents sensitive to smoke pollution should take precautions if local air quality deteriorates.