COEUR d’ALENE — Labor Day was not a good day for anyone to be laboring — or doing anything else outdoors in North Idaho.

Smoke from western wildfires blanketed the region Monday, progressively degrading the air quality to some of the unhealthiest levels categorized by environmental monitors.

By 6 p.m., the air quality index in the Coeur d’Alene area was at 303 and in the “hazardous” range, according to the Idaho Department of Environmental Quality’s air conditions monitoring station on Lancaster Road in Hayden.

Earlier in the day, the air quality went from “unhealthy” at noon to “very unhealthy” at 2 p.m.

The eye-stinging, sinus-irritating, visibility-limiting haze is not expected to begin improving until mid-week.

“Air quality is only expected to get worse as wind shifts bring in smoke from British Columbia and Montana fires, in addition to smoke from the Washington and Oregon Cascades,” said the National Weather Service in Spokane.

An air quality alert was issued Monday morning by the weather service and is expected to remain in effect until Wednesday at noon.

“The reason the smoke has gotten so bad … it’s coming in from three different directions, from southwest and northwest aloft and from the east and northeast at the surface,” said the weather service, on social media.

Smoke from wildfires is a health threat, according to the Idaho Department of Health and Welfare, because it is a mixture of gases and fine particles from burning trees and other plant materials.

When the air quality is categorized as “very unhealthy,” everyone may experience serious health effects, not just vulnerable populations like those with heart and lung conditions, children and the elderly

Air quality index values in the “hazardous” range trigger warnings for everyone with the entire population at greater risk for serious health effects.

Air conditions in Spokane and Sandpoint were also “hazardous” by Monday evening.

People in Kootenai County were likely playing it safe on Labor Day, staying indoors with the windows shut.

“We’re not seeing more people with respiratory issues than normal,” Kootenai Health spokesperson Kim Anderson said early Monday evening.

Anderson did note her daughter’s soccer practice was canceled earlier in the day.

There is some good news. The weather service is forecasting cooler temperatures by the end of the week, with highs of 80 to 82 degrees on Friday and Saturday in Coeur d’Alene.