Wildfire smoke Agency determination
Daily PM2.5 peaked at 513.4 µg/m³ near Portland across 3 covered metros home to 7.3 million people. 2 metros recorded their worst day on record; 3 placed a top-ten day.
Counting the extra PM2.5 above each metro's typical day, this event handed the average affected resident ≈ 68.9 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 502 million cigarettes. An awareness illustration of outdoor exposure at 22 µg/m³ per cigarette (Berkeley Earth), counting only the event's ranked days; not a medical dose.
Why we think this happened
Supplied qualified evidence supports wildfire-smoke as the root cause. The grouping includes only events linked by explicit shared episode evidence; otherwise this remains a single-event episode.
Agency determination A government body issued a record naming this cause for this event: an NWS air-quality alert, a NOAA Storm Events record, or a state or local official archive.
U.S. EPA Air Quality System and the submitting air monitoring agency · Sep 16, 2020 official
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 405 PM2.5 samples in the candidate CBSA on 2020-09-16, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
U.S. EPA Air Quality System and the submitting air monitoring agency · Sep 16, 2020 official
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 192 PM2.5 samples in the candidate CBSA on 2020-09-16, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
U.S. EPA Air Quality System and the submitting air monitoring agency · Sep 14, 2020 official
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 387 PM2.5 samples in the candidate CBSA on 2020-09-14, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
See every retained source and limitation ↓
Sequence: Portland (Sep 10) → Seattle (Sep 11) → Spokane (Sep 12)
Evidence path
A cause is more convincing when the record connects three things: something happened, the air mass moved toward the region, and local instruments responded. Here is how much of that chain is documented for this event.
Source or mechanism
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 405 PM2.5 samples in the candidate CBSA on 2020-09-16, identifying wildfire smoke as affecting the samples. An informational qualifier is an official…
View supporting source ↗Air-mass movement
Washington Ecology reports that smoke from Oregon wildfires moved into Washington beginning September 10 and that statewide PM2.5 monitors were above the federal 24-hour standard September 12-17.
View transport source ↗Local response
EPA monitors recorded the event across 3 metros. The peak daily concentration is roughly 23.3 cigarette-equivalents at the outdoor daily rate.
Inspect the pollutant and weather signals ↓Event autopsy
Before, during, and after the episode: nearby pollutant monitors and surface-weather stations show what changed. This context tests the “Wildfire smoke” explanation; it does not assign the cause by itself.
Portland-Vancouver-Hillsboro, OR-WA
Monitor comparison window 2020-09-07 to 2020-09-20 · PM2.5 target: Vancouver-NE 84th Ave
51% above nearby days
6% higher than surrounding days
94% higher than surrounding days
51% higher than surrounding days
94% higher than surrounding days
22% higher than surrounding days
110% higher than surrounding days
62% lower than surrounding days
About the same as surrounding days
About the same as surrounding days
About the same as surrounding days
6% higher than surrounding days
Seattle-Tacoma-Bellevue, WA
Monitor comparison window 2020-09-07 to 2020-09-20 · PM2.5 target: Tukwila Allentown
128% above nearby days
17% lower than surrounding days
60% higher than surrounding days
128% higher than surrounding days
60% higher than surrounding days
30% higher than surrounding days
About the same as surrounding days
15% lower than surrounding days
About the same as surrounding days
About the same as surrounding days
About the same as surrounding days
17% lower than surrounding days
Spokane-Spokane Valley, WA
Monitor comparison window 2020-09-09 to 2020-09-21 · PM2.5 target: Colville-E 1St
181% above nearby days
7% lower than surrounding days
117% higher than surrounding days
181% higher than surrounding days
117% higher than surrounding days
12% higher than surrounding days
About the same as surrounding days
7% lower than surrounding days
Source: U.S. EPA AirData daily observations and, where available, nearby ASOS/AWOS surface observations. Values are descriptive medians over the retained monitor set; missing measurements remain missing. Transport and source evidence remain separate layers because this instrument pattern does not assign a cause by itself.
Air-mass reconstruction
NOAA HYSPLIT traces the air arriving at each metro backward for 72 hours. Multiple arrival times and heights show whether the broad path is stable—or sensitive to assumptions about when and where the polluted layer arrived.
Air arriving near Portland-Vancouver-Hillsboro
Peak-date arrivals · 2020-09-13
Each line begins 72 hours before arrival and points toward the metro. Color represents arrival height; repeated lines represent 00, 06, 12, and 18 UTC arrival assumptions. A path can show where the air traveled, but it cannot prove which source added the PM2.5.
Air arriving near Seattle-Tacoma-Bellevue
Peak-date arrivals · 2020-09-14
Each line begins 72 hours before arrival and points toward the metro. Color represents arrival height; repeated lines represent 00, 06, 12, and 18 UTC arrival assumptions. A path can show where the air traveled, but it cannot prove which source added the PM2.5.
Air arriving near Spokane-Spokane Valley
Peak-date arrivals · 2020-09-13
Each line begins 72 hours before arrival and points toward the metro. Color represents arrival height; repeated lines represent 00, 06, 12, and 18 UTC arrival assumptions. A path can show where the air traveled, but it cannot prove which source added the PM2.5.
Episode peak
-- cigarettes
The smoke map's scale, replayed over this event: the surface interpolates between covered metros' daily records, framed to the affected region. Hover for a reading, click a metro to pin it to the card. Days a monitor did not report draw nothing.
Views from the selected metro
Select a metro on the map to see nearby cameras. Where an operator archive reaches the event, drag the divider to compare two moments, adjust either date and time, or play the available event-day frames. Camera imagery is visual context, not an air-quality measurement or proof of smoke.
No useful public camera views are currently available within 80 km of this metro.
| Metro | Peak PM2.5 | Cigarettes, whole event | Peak day | All-time standing |
|---|---|---|---|---|
| Portland-Vancouver-Hillsboro, OR-WA | 513.4 µg/m³ | 112.7 | Sep 13, 2020 | Worst day on record |
| Spokane-Spokane Valley, WA | 396.8 µg/m³ | 71.3 | Sep 13, 2020 | Worst day on record |
| Seattle-Tacoma-Bellevue, WA | 188.2 µg/m³ | 46.2 | Sep 14, 2020 | #2 of its top days |
"Cigarettes, whole event" totals a metro's ranked event days at 22 µg/m³ per cigarette: what a person outdoors there breathed across the event, as the illustration. "All-time standing" is where this episode's days sit in each metro's ranked record (worst-area measure, since 1999). Full local context is on each metro's Air Records page.
Public evidence library
Each card states what a source supports—and what it does not. Official records, research, reporting, community observations, and transparent inferences remain visibly different kinds of evidence.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 405 PM2.5 samples in the candidate CBSA on 2020-09-16, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 192 PM2.5 samples in the candidate CBSA on 2020-09-16, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 387 PM2.5 samples in the candidate CBSA on 2020-09-14, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 404 PM2.5 samples in the candidate CBSA on 2020-09-15, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 384 PM2.5 samples in the candidate CBSA on 2020-09-13, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 195 PM2.5 samples in the candidate CBSA on 2020-09-15, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 192 PM2.5 samples in the candidate CBSA on 2020-09-10, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 218 PM2.5 samples in the candidate CBSA on 2020-09-12, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 192 PM2.5 samples in the candidate CBSA on 2020-09-17, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 214 PM2.5 samples in the candidate CBSA on 2020-09-14, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 228 PM2.5 samples in the candidate CBSA on 2020-09-13, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 374 PM2.5 samples in the candidate CBSA on 2020-09-10, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 386 PM2.5 samples in the candidate CBSA on 2020-09-12, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 408 PM2.5 samples in the candidate CBSA on 2020-09-17, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 371 PM2.5 samples in the candidate CBSA on 2020-09-11, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 197 PM2.5 samples in the candidate CBSA on 2020-09-11, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 119 PM2.5 samples in the candidate CBSA on 2020-09-12, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 120 PM2.5 samples in the candidate CBSA on 2020-09-14, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 120 PM2.5 samples in the candidate CBSA on 2020-09-17, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 119 PM2.5 samples in the candidate CBSA on 2020-09-18, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 120 PM2.5 samples in the candidate CBSA on 2020-09-15, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 120 PM2.5 samples in the candidate CBSA on 2020-09-16, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 120 PM2.5 samples in the candidate CBSA on 2020-09-13, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
An archived NWS Air Quality Alert for Seattle-Tacoma-Bellevue, WA, issued 2020-09-08T10:20Z, explicitly identifies wildfire smoke. IEM is the archive, not the official system of record.
An archived NWS Air Quality Alert for Spokane-Spokane Valley, WA, issued 2020-09-14T17:55Z, explicitly identifies wildfire smoke. IEM is the archive, not the official system of record.
NWS Dense Smoke record, SPOKANE AREA, WASHINGTON (2020-09-12)
An air quality sensor in Spokane recorded unhealthy air quality from September 12th through 19th. It spiked to continuous hazardous conditions on September 13th through 15th.
NWS Dense Smoke record, WASHINGTON PALOUSE, WASHINGTON (2020-09-12)
An air quality sensor in Pullman recorded unhealthy air quality from September 12th through September 19th. It spiked to continuous hazardous conditions on September 13th through 15th.
NWS Dense Smoke record, WENATCHEE AREA, WASHINGTON (2020-09-12)
An air quality sensor in Wenatchee recorded unhealthy air quality from September 12th through September 19th. Thick smoke dispersed a little on September 15th with the arrival of a weak front and wind shift.
NWS Dense Smoke record, OKANOGAN VALLEY, WASHINGTON (2020-09-12)
An air quality sensor at Omak recorded unhealthy air quality from September 12th through September 19th with occasional spikes into the Very Unhealthy and Hazardous categories.
NWS Dense Smoke record, UPPER COLUMBIA BASIN, WASHINGTON (2020-09-12)
An air quality sensor in Ritzville recorded unhealthy air quality from September 12th through September 19th with spikes into the Very Unhealthy and Hazardous categories.
NWS Dense Smoke record, NORTHEAST MOUNTAINS, WASHINGTON (2020-09-12)
An air quality sensor in Colville recorded unhealthy air quality from September 12th through September 19th with occasional spikes into the Very Unhealthy and Hazardous categories.
NWS Dense Smoke record, SEATTLE AND VICINITY, WASHINGTON (2020-09-11)
The ignition of multiple wildfires across the Pacific Northwest around Labor Day led to a period of poor air quality by mid-September as dense smoke combined with low level moisture and fog.
Washington Ecology reports that smoke from Oregon wildfires moved into Washington beginning September 10 and that statewide PM2.5 monitors were above the federal 24-hour standard September 12-17.
Air quality update: Advisory lifted for Oregon Coast, smoke to remain elsewhere next couple of days
Oregon DEQ attributed the Portland-Vancouver regional advisory to smoke from fires in Oregon, Washington, and California and reported recent hazardous-to-very-unhealthy smoke levels.
Joint press release: Wildfire Smoke
Regional agency press release identifies wildfire smoke as the cause of the September health alert in Washington.
Agency determination A government body issued a record naming this cause for this event: an NWS air-quality alert, a NOAA Storm Events record, or a state or local official archive.
This episode was grouped from the monitor record by the catalog pipeline and given its cause from the evidence listed above. It has not been individually reviewed and signed off, so its boundaries, cause, and name may change as evidence accumulates. Grouping policy common_sense_root_cause_grouping.v2. The cause label reflects the assembled evidence above, not an IAQng detection formula. If it is wrong, tell us.