Air Quality Index soared above 200 in Boise area Friday. How long will the smoke stay?

An air quality advisory was sent out for the Treasure Valley on Friday afternoon, as smoke blew in from the massive wildfires burning in the Boise National Forest.

Les Colin with the National Weather Service said the air quality advisory will continue until 3 p.m. Tuesday.

The Idaho Department of Environmental Quality’s air quality map showed readings over 200 in Garden City and Meridian at times Friday. Over 200 is the purple (very unhealthy) category.

“(The smoke is) draining. It’s draining from higher elevations down to lower so it is draining to the south and to the west toward us,” Colin said. “Draining is done by gravity, but it can be influenced by the actual wind. The wind is light, and so gravity is directing most of this draining. So it’s draining downward from higher elevations to lower and that’s allowing it to get into these valleys.”

Colin said the air quality index over Boise as of noon Friday was 155 (red). The air quality advisory affects Ada, Adams, Boise, Canyon, Elmore, Gem, Owyhee, Payette, Valley and Washington counties, according to the National Weather Service.

The advisory suggests those with respiratory problems who are sensitive to smoke avoid long outdoor activities, and open burning is prohibited by air quality rules. The pollution can also cause breathing difficulties for children and the elderly.

Many high school sporting events have been canceled or rescheduled as a result of the smoke. The Boise School District moved its Friday varsity football doubleheader (Borah-Timberline, Boise-Capital) to Homedale to try to find cleaner air.

The lightning-caused Wapiti Fire has scorched nearly 92,000 acres in Custer County and remained uncontained as of Friday. The fire increased tenfold in size in a little over a week — it was 9,000 acres on Aug. 20. More than 800 personnel are working to contain it.

The Nellie Fire is part of the Middle Fork Complex and has spread to nearly 53,000 acres with only 6% containment, so both fires will continue to pour out smoke.

This story was originally published August 30, 2024 at 4:18 PM.