Wildfire smoke
September 9–11, 2024 Southern California wildfire-smoke episode
Daily PM2.5 peaked at 85.9 µg/m³ near Riverside across 2 covered metros home to 7.1 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 ≈ 3.2 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 23 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
The supplied evidence supports wildfire smoke and documents an overlapping or continuing regional occurrence across the proposed members. The supplied evidence supports wildfire smoke and documents an overlapping or continuing regional occurrence across the proposed members.
Sequence: Riverside (Sep 9) → Las Vegas (Sep 11)
Affected metros
| Metro | Peak PM2.5 | Cigarettes, whole event | Peak day | All-time standing |
|---|---|---|---|---|
| Riverside-San Bernardino-Ontario, CA | 85.9 µg/m³ | 3.9 | Sep 9, 2024 | #18 of its top days |
| Las Vegas-Henderson-Paradise, NV | 83.3 µg/m³ | 3.8 | Sep 11, 2024 | #3 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 Wildfire, CALIFORNIA, Sep 5, 2024 "Following and during a record heat wave, 3 large wildfires erupted and became out of control burning rapidly. The Airport fire started in Trabuco Canyon in Orange County on the south portion of the Santa Ana mountains. T…" record →
EPA AQS monitor qualifier 2
- AQS PM2.5 qualifier IT — Wildfire-U. S. EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 97 PM2.5 samples in the candidate CBSA on 2024-09-09, 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 336 PM2.5 samples in the candidate CBSA on 2024-09-11, 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.
NWS Air Quality Alert 1
- Archived Riverside-area Air Quality Alert, September 9, 2024 South Coast AQMD explicitly attributed increased fine-particle pollution in the Riverside event area to wildfire smoke. IEM is the archive, not the official system of record.
Agency and publisher pages 2
- Riverside County Health Officials Urge Residents to Take Precautions Due to Smoke and Ash from Fires Riverside County stated that Southern California wildfires were generating smoke and ash over parts of the county during the event period.
- Air Quality Alert for Wildfire Smoke Issued Through and Friday Clark County reported that smoke from Southern California wildfires was lingering in the Las Vegas Valley and elevating particulate matter.
What remains uncertain
- The supplied evidence does not identify or quantify every specific source contributing across all proposed members.
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.