When it comes to air quality, it’s not easy being green during fire season

The Boise skyline was covered by a haze Friday afternoon.
The Boise skyline was covered by a haze Friday afternoon. kmoeller@idahostatesman.com

Yellow. Orange. Red. Purple. Maroon.

Idaho’s air quality alert system, created by the U.S. Environmental Protection Agency, has a rainbow of colors to denote how healthy — or unhealthy — the air is. It doesn’t have the one color that we see when summer wildfires are raging in the West: gray.

The Boise area is being blanketed by smoke from the Cinder Butte Fire in eastern Oregon and a half-dozen major wildfires raging in that state. Cinder Butte has burned more than 52,000 acres in Harney County since Wednesday, and fire officials at InciWeb said it was only 9 percent contained Friday.

Green, not sky blue, means good air quality. In fact, blue isn’t part of the EPA’s color scale. No matter. Boise will be in the yellow again this weekend — a tad better than the orange we had Thursday and Friday, according to the Idaho Department of Environmental Quality, and similar to what many July days were.

But the air quality could deteriorate. There’s a new Oregon blaze, the Morgan Creek Fire in Baker County, and a huge amount of smoke from fires in British Columbia is being carried this direction by winds out of the northwest.

An upper-level storm out of the southwest Saturday night might keep the smoke from fires northwest of us from having a significant impact on the Treasure Valley, National Weather Service meteorologist Stephen Parker said.

Very yellow July

July 2017 was largely yellow for Boise, meaning moderate levels of pollution for 20 days. Three days were in the orange range, or unhealthy for sensitive groups, such as the elderly, children or those with lung or heart conditions.

That’s significantly more days of polluted air in July than the past two summers, according to Idaho Department of Environmental Quality data. We had 13 days in the yellow in July 2016 and just four days in the yellow in 2015 (and all the rest were green).

“The air quality levels we’ve seen this July and into August are not really out of the norm for what we’d expect to see at this time of year,” said Michael Toole, regional airshed coordinator for the DEQ in Boise.

Ozone levels were as much or more of a factor in the poor air quality in July than wildfire smoke, he said. Hot temperatures, clear skies and stagnant weather can drive up ozone formation. Also, light smoke can enhance ozone formation.

‘We have really good air quality’

August is the summer month in which Boise typically sees the most yellow, orange and red alerts. But we see those alerts in the winter months, too, when inversions can trap cold air and pollution on the Treasure Valley floor.

If all of this makes you feel blue, consider this:

“Overall, we have really good air quality,” Toole said. “People just remember these events. We’re 75 percent in the green.”

Katy Moeller: 208-377-6413, @KatyMoeller