Portland, OR Air Quality & Smog

Dominant pollutants, when smog is worst, notable historical episodes, and local agency resources for Portland, OR — plus how to check the current AQI. For real-time readings, the free Smog Report iOS app pulls live air quality from EPA AirNow.

Dominant pollutants

PM2.5 (wildfire smoke summer + winter wood smoke), low ozone year-round.

Seasonal pattern: when smog is worst

Portland's air quality is normally excellent thanks to marine ventilation. The exception is wildfire season — smoke from Eastern Oregon fires and California transport regularly pushes PM2.5 to Unhealthy or Hazardous for days at a time. Winter wood smoke from residential heating accumulates during inversion episodes in the Willamette Valley.

A recent or notable event

September 2020 — the Beachie Creek and Riverside Fires combined to push Portland's AQI past 500 (off-the-chart Hazardous), the worst air quality of any major city in the world for several days.

Local agencies and resources

Oregon DEQ runs the AirNow monitors.

• Oregon Department of Environmental Quality (DEQ)
• Multnomah County Health Department

How to check air quality in Portland

The EPA's AirNow.gov publishes the canonical reading from the nearest regulatory monitor. For glanceable iPhone access — including widgets, Live Activities, Siri voice queries, and Apple Watch — install Smog Report. It's free, requires no account, and pulls from the same AirNow API.

For Portland-specific advisories and alerts that go beyond the federal AirNow feed, check the agency pages above directly.

Common questions about Portland air quality

Why does Portland have air-quality and smog problems?

Portland's air quality is normally excellent thanks to marine ventilation. The exception is wildfire season — smoke from Eastern Oregon fires and California transport regularly pushes PM2.5 to Unhealthy or Hazardous for days at a time. Winter wood smoke from residential heating accumulates during inversion episodes in the Willamette Valley.

What are the main air pollutants in Portland?

Portland's dominant pollutants are PM2.5 (wildfire smoke summer + winter wood smoke), low ozone year-round. The AQI on any given day is usually driven by whichever of these is highest.

Has Portland had a major air-quality or smog event?

September 2020 — the Beachie Creek and Riverside Fires combined to push Portland's AQI past 500 (off-the-chart Hazardous), the worst air quality of any major city in the world for several days.

How can I check Portland's air quality right now?

The EPA's AirNow.gov publishes the official reading from the nearest regulatory monitor. For live AQI on your iPhone — with home-screen widgets, Lock Screen Live Activities, Siri, and Apple Watch — the free Smog Report app pulls from the same AirNow feed. No account is required.

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