Wildfire smoke
June 3–6, 2025 Upper Midwest Canadian wildfire-smoke episode
Daily PM2.5 peaked at 93.5 µg/m³ near Minneapolis across 6 covered metros home to 20 million people. 2 metros 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 ≈ 2.4 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 48 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. The supplied evidence supports wildfire smoke and documents an overlapping or continuing regional occurrence across the proposed members.
Sequence: Minneapolis (Jun 3) → Milwaukee (Jun 4) → Madison (Jun 4) → Chicago (Jun 5) → Detroit (Jun 6) → Toledo (Jun 6)
Affected metros
| Metro | Peak PM2.5 | Cigarettes, whole event | Peak day | All-time standing |
|---|---|---|---|---|
| Minneapolis-St. Paul-Bloomington, MN-WI | 93.5 µg/m³ | 4.3 | Jun 3, 2025 | #5 of its top days |
| Chicago-Naperville-Elgin, IL-IN-WI | 59.4 µg/m³ | 2.7 | Jun 5, 2025 | #21 of its top days |
| Detroit-Warren-Dearborn, MI | 56.3 µg/m³ | 2.6 | Jun 6, 2025 | #20 of its top days |
| Milwaukee-Waukesha-West Allis, WI | 51.2 µg/m³ | 2.3 | Jun 4, 2025 | #14 of its top days |
| Madison, WI | 49.8 µg/m³ | 2.3 | Jun 4, 2025 | #12 of its top days |
| Toledo, OH | 49.6 µg/m³ | 2.3 | Jun 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.
The evidence
EPA AQS monitor qualifier 8
- AQS PM2.5 qualifier IF — Fire - Canadian. EPA AQS carries an agency-submitted informational qualifier (IF, Fire - Canadian.) on 312 PM2.5 samples in the candidate CBSA on 2025-06-03, 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 76 PM2.5 samples in the candidate CBSA on 2025-06-05, 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 20 PM2.5 samples in the candidate CBSA on 2025-06-05, 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 452 PM2.5 samples in the candidate CBSA on 2025-06-05, 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 45 PM2.5 samples in the candidate CBSA on 2025-06-04, 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 96 PM2.5 samples in the candidate CBSA on 2025-06-04, 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 429 PM2.5 samples in the candidate CBSA on 2025-06-04, 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 75 PM2.5 samples in the candidate CBSA on 2025-06-06, 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
- Southeast Michigan PM2.5 advisory due to wildfire smoke Michigan EGLE continued a June 6 fine-particle advisory for southeast Michigan and explicitly attributed elevated PM2.5 to wildfire smoke; this directly covers the Detroit member. IEM is the archive, not the official system of record.
Agency and publisher pages 3
- Air quality alert due to wildfire smoke continues through Wednesday, June 4, for southern, central, north central, and northeast Minnesota MPCA attributed the Twin Cities-area air-quality alert covering June 3 to wildfire smoke.
- DNR Recommends Wisconsinites Limit Time Outside Due To Canadian Wildfire Smoke Wisconsin DNR attributed the June 3–4 advisory to Canadian wildfire smoke moving northwest to southeast across Wisconsin.
- Air quality advisory in effect for Southeast Michigan due to Canadian wildfire smoke Local reporting relayed EGLE's advisory for elevated PM2.5 from Canadian wildfire smoke through June 6 in southeast Michigan, including the Detroit-area portion of this event.
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.