Wildfire smoke
July 30–August 5, 2025 Midwest Canadian wildfire-smoke episode
Daily PM2.5 peaked at 89.8 µg/m³ near Milwaukee across 11 covered metros home to 29 million people. 8 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 ≈ 4.0 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 115 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. 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 a
Sequence: Minneapolis (Jul 30) → Milwaukee (Jul 31) → Madison (Jul 31) → Chicago (Jul 31) → Grand Rapids (Jul 31) → Des Moines (Jul 31) → Kansas City (Aug 1) → St. Louis (Aug 1) → Omaha (Aug 1) → Wichita (Aug 1) → +1 more metros
Affected metros
| Metro | Peak PM2.5 | Cigarettes, whole event | Peak day | All-time standing |
|---|---|---|---|---|
| Milwaukee-Waukesha-West Allis, WI | 89.8 µg/m³ | 12.0 | Jul 31, 2025 | #7 of its top days |
| Minneapolis-St. Paul-Bloomington, MN-WI | 87.1 µg/m³ | 10.4 | Aug 1, 2025 | #7 of its top days |
| Madison, WI | 83 µg/m³ | 3.8 | Jul 31, 2025 | #7 of its top days |
| Chicago-Naperville-Elgin, IL-IN-WI | 79.1 µg/m³ | 3.6 | Jul 31, 2025 | #8 of its top days |
| Grand Rapids-Wyoming, MI | 72.4 µg/m³ | 5.8 | Jul 31, 2025 | #7 of its top days |
| Kansas City, MO-KS | 63.8 µg/m³ | 4.8 | Aug 1, 2025 | #4 of its top days |
| Detroit-Warren-Dearborn, MI | 57.6 µg/m³ | 2.6 | Aug 4, 2025 | #18 of its top days |
| St. Louis, MO-IL | 52.1 µg/m³ | 2.4 | Aug 1, 2025 | #12 of its top days |
| Omaha-Council Bluffs, NE-IA | 50 µg/m³ | 2.3 | Aug 1, 2025 | #10 of its top days |
| Des Moines-West Des Moines, IA | 49.7 µg/m³ | 4.3 | Jul 31, 2025 | #7 of its top days |
| Wichita, KS | 39 µg/m³ | 3.4 | Aug 1, 2025 | #17 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 18
- AQS PM2.5 qualifier IF — Fire - Canadian. EPA AQS carries an agency-submitted informational qualifier (IF, Fire - Canadian.) on 264 PM2.5 samples in the candidate CBSA on 2025-07-30, 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 264 PM2.5 samples in the candidate CBSA on 2025-07-31, 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 264 PM2.5 samples in the candidate CBSA on 2025-08-01, 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 456 PM2.5 samples in the candidate CBSA on 2025-07-31, 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 2025-07-31, 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 2025-08-01, 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 95 PM2.5 samples in the candidate CBSA on 2025-08-01, 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 2025-08-02, 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 79 PM2.5 samples in the candidate CBSA on 2025-07-31, 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 10 PM2.5 samples in the candidate CBSA on 2025-07-31, 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 2025-08-02, 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 2025-07-31, 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.
- +6 more EPA AQS records on file
NWS Air Quality Alert 4
- Wisconsin PM2.5 alert for Canadian wildfire smoke Wisconsin's July 31 alert attributed unhealthy surface-level PM2.5 to Canadian wildfire smoke, directly covering the Milwaukee member of the multi-place event. IEM is the archive, not the official system of record.
- Illinois August 1 Air Pollution Action Day due to wildfire smoke The archived alert relayed Illinois EPA's August 1 statewide action day for wildfire smoke, applying to the Illinois portion of the St. Louis metro. IEM is the archive, not the official system of record.
- Wisconsin weekend air-quality alert for Canadian wildfire smoke Wisconsin's August 2 alert said Canadian wildfire smoke would continue to affect surface air quality through the weekend, directly covering Milwaukee. IEM is the archive, not the official system of record.
- Wisconsin air-quality alert for Canadian wildfire smoke Wisconsin's August 5 alert said Canadian wildfire smoke would continue affecting surface air quality into Wednesday morning, directly covering Milwaukee. IEM is the archive, not the official system of record.
Agency and publisher pages 7
- Wisconsinites: Limit Time Outside Due To Canadian Wildfire Smoke Wisconsin DNR attributed widespread unhealthy PM2.5 conditions on July 31 to Canadian wildfire smoke; this directly covers the Milwaukee portion of the event.
- DHHS/DWEE Issues Smoke Advisory for Eastern and Central Nebraska Nebraska's smoke advisory identified Canadian wildfire smoke affecting eastern Nebraska, including Omaha, from August 1 into August 2.
- KDHE Issues Air Quality Health Advisory due to Smoke KDHE attributed the August 1 advisory in central and eastern Kansas to Canadian wildfire smoke transported by northeast to east winds.
- MPCA issues MN's longest-ever air quality alert for Canadian wildfire smoke Local reporting described MPCA's alert through August 2 as caused by northwesterly transport of Canadian wildfire smoke into Minnesota.
- Smoke from Canadian wildfires brings unhealthy air to large swaths of the Midwest Associated Press reported Canadian wildfire-smoke alerts across the connected Midwest episode, including Iowa and eastern Nebraska, with smoke forecast to spread into Missouri.
- Canadian wildfire smoke triggers Wayne County’s 16th air quality alert of 2025 Reporting on Michigan's statewide fine-particle advisory says an EGLE air-quality meteorologist identified Canadian wildfire smoke as the driver; Detroit conditions were reported as unhealthy on August 4.
- Canadian wildfire smoke extends Wisconsin air quality advisory The report says Wisconsin's air-quality advisory, including the Milwaukee area, was extended through August 5 because Canadian wildfire smoke was affecting surface air quality; it identifies PM2.5 as the relevant small-particle pollutant.
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.