The National Weather Service on Monday extended an air stagnation advisory for much of the Inland Northwest through noon today.
Meanwhile, air quality agencies were keeping an eye on elevated pollution levels, caused mostly by wood smoke.
The Idaho Department of Environmental Quality imposed an outdoor burn ban in the Coeur d’Alene area Monday and asked residents to not burn indoors as air quality deteriorated from good to moderate there.
In Spokane, agricultural burning is banned, but residents are allowed to burn indoors despite air pollution levels in the moderate category.
In the Colville area, the state Department of Ecology has imposed a more stringent, stage 2 indoor burn ban, which prohibits the use of indoor wood stoves and fireplaces, even those certified to produce less pollution. However, indoor burning is allowed in homes where wood is the main source of heat.
Karen Wood, Ecology’s regional manager of air quality, said the elevated pollution was aggravated by widespread outdoor burning of unwanted vegetation over the weekend across the Inland Northwest. There were also a significant number of recreational fires, she said.
Air quality is expected to improve today and Wednesday as winds blow in from the west and southwest.
The Pacific Northwest is subject to higher pollution levels in autumn and fall. Cold, still nights create a situation where air closer to the ground is colder than it is higher up, a reverse of the normal pattern. The so-called temperature inversion creates what amounts to a blanket of dirty, cold air at the Earth’s surface that stays in place until a storm scours it away.
On Thursday, cold winds could set the stage for light snow, forecasters said, but another ridge of high pressure is expected by Sunday.
Changes in federal air quality laws two years ago reduced the allowable level of smoke-size particles in the air to 35 micrograms per cubic liter of air, down from 65 micrograms. That means the region is likely to see more burn bans than in previous years, Wood said.