BOISE, Idaho — Idaho continues to have some of the worst air quality in the United States.
Thursday morning, air quality in the Treasure Valley was hazardous, which is the highest category on the Air Quality Index. Hazardous is considered a health warning of emergency conditions and everyone is more likely to be affected.
Mike Toole, the Regional Airshed Coordinator for the Idaho Department of Environmental Quality, said the data showing the hazardous air is preliminary but does show that hazardous air conditions were present in Meridian for two hours in the morning.
"It's not impossible, but it's rare. And I would say that we don't even see that every fire season. It would be hard to say how often it happens," he said.
Additionally, unofficial air quality sensors showed hazardous air for several hours in Southeast Boise before conditions slowly improved throughout the day.
Toole explained the conditions set the stage for the very high concentrations of smoke.
"We have a lot of smoke from area fires that drained into the area. We had a new fire overnight where none of that smoke could escape," he said.
Toole continued that under a high-pressure ridge, smoke tends to remain stagnant.
"It kind of just swirls around, and so what you'll see is a pocket of denser smoke with a higher concentration, almost like an encapsulated plume that moves around," he said. "It seems like it went right through Meridian this morning and sent those concentrations sky-high."
The Treasure Valley's reaching the hazardous category was new. But parts of the Boise and Central mountains have been dealing with hazardous air for the past month or so.
The 2024 wildfire season continues to be comparable to other busy wildfire seasons like 2021 and 2017. In 2021, Treasure Valley areas saw wildfire smoke until October.