Wildfire smoke Documented
Daily PM2.5 peaked at 168.1 µg/m³ near Spokane across 1 covered metro home to 604,962 people. 1 metro placed a top-ten day in their record.
Counting the extra PM2.5 above each metro's typical day, this event handed the average affected resident ≈ 17.5 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 11 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
The supplied retained evidence supports wildfire smoke for this event; no supplied evidence establishes membership in a broader time-bounded episode.
Documented An agency or publisher page assesses this cause, without an agency record naming the event or an EPA qualifier on the data.
Spokane Regional Health District · Sep 3, 2025 official
The Spokane Regional Clean Air Agency, through the regional health district notice, attributed worsening Spokane air quality to smoke from regional wildfires combined with poor overnight ventilation.
Spokane Public Radio · Sep 4, 2025 corroborates
A National Weather Service meteorologist said smoke and haze would persist in Spokane; the report identified fires in Stevens and Ferry counties, British Columbia, and northwest Montana as the principal regional smoke sources.
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
The Spokane Regional Clean Air Agency, through the regional health district notice, attributed worsening Spokane air quality to smoke from regional wildfires combined with poor overnight ventilation.
View supporting source ↗Air-mass movement
A National Weather Service meteorologist said smoke and haze would persist in Spokane; the report identified fires in Stevens and Ferry counties, British Columbia, and northwest Montana as the principal regional smoke sources.
View transport source ↗Local response
EPA monitors recorded the event across 1 metro. The peak daily concentration is roughly 7.6 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.
Spokane-Spokane Valley, WA
Monitor comparison window 2025-09-01 to 2025-09-09 · PM2.5 target: Colville-E 1St
90% above nearby days
30% lower than surrounding days
80% higher than surrounding days
90% higher than surrounding days
80% higher than surrounding days
About the same as surrounding days
6% lower than surrounding days
30% 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.
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 |
|---|---|---|---|---|
| Spokane-Spokane Valley, WA | 168.1 µg/m³ | 18.5 | Sep 6, 2025 | #10 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.
Wildfire smoke affecting local air quality
The Spokane Regional Clean Air Agency, through the regional health district notice, attributed worsening Spokane air quality to smoke from regional wildfires combined with poor overnight ventilation.
Unhealthy air quality to persist over the weekend with ongoing wildfires across the region
A National Weather Service meteorologist said smoke and haze would persist in Spokane; the report identified fires in Stevens and Ferry counties, British Columbia, and northwest Montana as the principal regional smoke sources.
Documented An agency or publisher page assesses this cause, without an agency record naming the event or an EPA qualifier on the data.
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.