High heat and choking wildfire smoke combined to create exceptionally unhealthy air quality throughout the West Coast on Thursday, September 1, 2022.

Baking temperatures across a wide swathe of the American landscape are contributing to poor air quality conditions across an unusually large geographic area. The Western U.S. has endured major air quality events from huge wildfires in the Pacific Northwest and California in previous years. But numerous medium to large acreage fires and high levels of ozone appear to be converging to worsen air quality from San Diego to Canada.

Air quality across the Pacific Northwest and Canada was poor on Thursday, September 1, 2022. Source: IQAir.

In California, wildfires polluted the skies across nearly the entire state, especially in Yosemite National Park. An air quality monitoring station in Yellowstone Village measured hazardous concentrations of PM2.5, as high as 414 microns per cubic meter of air (µg/m3) at 11 am on Thursday. PM2.5 is particulate matter measuring less than 2.5 microns in diameter.

Large-scale wildfires burned north and south of Medford, Oregon. High heat and wildfire smoke also influenced poor air quality conditions in Washington State, Idaho, and British Columbia, Canada.

Heat wave descends on American West and Southwest

An extreme and prolonged heat wave broiled the American Southwest on Thursday afternoon. Temperatures were forecast to range from 95 to 113 degrees Fahrenheit in Arizona, California, Idaho, Nevada, Oregon, and Utah (1).

An excessive heat warning was issued by the National Weather Service for most of California, Phoenix, Arizona, and southern Nevada (2). Parts of Idaho, Oregon, Nevada, Washington state, and Montana were all placed under heat advisories and fire weather watches.

The heat wave is expected to last through Labor Day weekend and early into Monday.

Where there’s excessive heat, there’s often poor air quality. Dry foliage becomes tinder, easily sparked by human activity or lighting strikes. Near cities, small-scale fires can worsen local air quality, while rural areas with miles of brush can become major conflagrations.

Wildfire smoke carries the airborne pollutant PM2.5 to human lungs, causing health illnesses like heart and lung disease.

Heat also generates high levels of surface ozone, a pollutant. Vehicle and industrial emissions in cities can chemically combine with sunlight to generate ozone, or smog.

Air quality alerts were issued in many communities in the western U.S., including the Willamette Valley, Oregon and Sacramento, California (3)(4).

Wildfire smoke converges in Pacific Northwest

The large number of wildfires in the Pacific Northwest saw most of the states and provinces in the region struggling with poor air quality.

Wildfires near Grants Pass and Medford, Oregon billowed wildfire smoke across the town.

Unhealthy to hazardous air quality measured near Grants Pass and Medford, Oregon. Source: IQAir.

Two major fires, one to the west of the cities and one to the north, both harmed regional air quality. The Rum Creek fire west of Grants Pass was nearly 15,000 acres and only 1 percent contained on Thursday, while the Cedar Creek fire covered 8,817 acres and was 12 percent contained (5)(6).

At 1 PM, Thursday, concentrations of PM2.5 measured in Grants Pass averaged a very unhealthy 153 µg/m3.

Dangerous air quality measured in Northern California near the Oregon border. Source: IQAir.

Similar wildfire smoke conditions occurred in Idaho, where wildfires near Boise led to polluted skies. A dozen wildfires north of the city, including the partially controlled 99,000-acre Moose fire, spewed smoke across Idaho and into neighboring states (7).

Elsewhere in the Pacific Northwest, wildfire smoke threatened air quality in towns along the eastern Cascades in Washington State.

Poor air quality measured in communities east of the Cascades in Washington State. Source: IQAir.

The small town of Winthrop experienced air quality designated “Unhealthy for Sensitive Groups,” a US air quality index of 103. The corresponding PM2.5 concentration was 36 µg/m3.

Air quality in Pacific Northwest communities like Bend, Oregon and Willow Creek, California ranged from unhealthy to hazardous.

Yosemite wildfires create hazardous air quality

Some of the worst air quality in the country was measured in Yosemite.

Hazardous air quality measured near wildfires in Yosemite Valley. Source: IQAir.

The Red and Rodgers fires, covering 3,558 acres and 1,644 acres respectively, created wildfire smoke in the national park and hazardous air quality (8)(9).

Wildfires frequently lead to smoky conditions in the park, causing it at times to be one of the worst vacation spots for air quality.

Wildfire burns outside of Los Angeles

The Route fire northwest of Los Angeles exploded to 5,200 acres as the heatwave began on August 31 (10)(11). The fire put the town of Castaic in danger from both fire and smoke. Wildfire smoke also drifted towards Santa Clarita and Los Angeles.

Excessive heat caused most of Los Angeles to experience “moderate” air quality. Source: IQAir.

High heat had already placed Los Angeles, Orange, Riverside, and San Bernardino Counties under an ozone advisory (12).

The takeaway

West Coast wildfires are becoming more common with our changing climate. Until source air pollutants are controlled to help mitigate climate change, there will be more heat waves to fuel dry conditions. That will in turn lead to more fire and smoke threatening the region.

When smoke endangers your community’s health, know if your air quality is poor by downloading a free air quality app. If the air is smoky and polluted, close your windows and run a high-performance air purifier.