Wildfire smoke
2023 mid-August Canadian wildfire-smoke episode
Named sources Gray Fire 10,064 acres , WA · IRWIN 2023-WANES-001974 Ridge Creek Fire 4,474 acres , ID · IRWIN 2023-IDIPF-000447 Oregon Road Fire
Daily PM2.5 peaked at 239.7 µg/m³ near Spokane across 2 covered metros home to 4.8 million 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 ≈ 5.4 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 26 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.
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.
What happened, in the record
Qualified supplied evidence supports wildfire smoke for this event. It is grouped with 1 other supplied event because the evidence identifies Canada as the shared origin and the affected intervals form one continuous 2023-08-19 through 2023-08-20 occurrence. Qualified supplied evidence supports wildfire smoke for this event. It is grouped with 1 other supplied event because the evidence identifies Canada as the shared origin and the affected intervals form one continuous 2023-08-19 through 2023-08-20 occurrence.
Sequence: Spokane (Aug 19) → Seattle (Aug 20)
Affected metros
| Metro | Peak PM2.5 | Cigarettes, whole event | Peak day | All-time standing |
|---|---|---|---|---|
| Spokane-Spokane Valley, WA | 239.7 µg/m³ | 18.3 | Aug 19, 2023 | #4 of its top days |
| Seattle-Tacoma-Bellevue, WA | 89.4 µg/m³ | 4.1 | Aug 20, 2023 | #15 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.
The evidence
Official records
- NOAA Storm Events Dust Storm, ARIZONA, Aug 20, 2023 "While the heaviest rainfall and flash flooding remained to the west across southern California, Tropical Storm Hilary did bring very strong winds to parts of southwest Arizona, which also led to areas of dense blowing du…" record →
EPA AQS monitor qualifier 3
- AQS PM2.5 qualifier IF — Fire - Canadian. EPA AQS carries an agency-submitted informational qualifier (IF, Fire - Canadian.) on 48 PM2.5 samples in the candidate CBSA on 2023-08-19, 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 IF — Fire - Canadian. EPA AQS carries an agency-submitted informational qualifier (IF, Fire - Canadian.) on 48 PM2.5 samples in the candidate CBSA on 2023-08-20, 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 IF — Fire - Canadian. EPA AQS carries an agency-submitted informational qualifier (IF, Fire - Canadian.) on 240 PM2.5 samples in the candidate CBSA on 2023-08-20, 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.
NWS Air Quality Alert 1
- Archived Spokane Air Quality Alert, August 19, 2023 The multi-agency Spokane alerts explicitly attributed the episode to smoke from local and Canadian wildfires. IEM is the archive, not the official system of record.
Agency and publisher pages 3
- Air Quality Report - August 2023 The regional clean-air agency attributes hazardous Spokane-area conditions on August 19–20 to widespread British Columbia fires and local Gray, Oregon Road, and Ridge Creek fires.
- OEM - Wildfire Smoke and Air Quality Guidance Seattle issued wildfire-smoke and air-quality guidance immediately before the August 20 event.
- News Releases for Saturday, August 19, 2023 The City of Spokane announced safer-air options because of heavy smoke on August 19.
Status and provenance
Research preview: this record carries research-only status and its boundaries, cause, and name may change as evidence review completes. Grouping policy common_sense_root_cause_grouping.v2. The cause label reflects the assembled evidence above, not an IAQng detection formula.