Wildfire smoke Agency determination
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.
Why we think this happened
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
Agency determination A government body issued a record naming this cause for this event: an NWS air-quality alert, a NOAA Storm Events record, or a state or local official archive.
U.S. EPA Air Quality System and the submitting air monitoring agency · Jul 30, 2025 official
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.
U.S. EPA Air Quality System and the submitting air monitoring agency · Jul 31, 2025 official
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.
U.S. EPA Air Quality System and the submitting air monitoring agency · Aug 1, 2025 official
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.
See every retained source and limitation ↓
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
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
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…
View supporting source ↗Air-mass movement
Nebraska's smoke advisory identified Canadian wildfire smoke affecting eastern Nebraska, including Omaha, from August 1 into August 2.
View transport source ↗Local response
EPA monitors recorded the event across 11 metros. The peak daily concentration is roughly 4.1 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.
Chicago-Naperville-Elgin, IL-IN-WI
Monitor comparison window 2025-07-28 to 2025-08-03 · PM2.5 target: IEPA TRAILER
151% above nearby days
151% higher than surrounding days
97% higher than surrounding days
151% higher than surrounding days
97% higher than surrounding days
17% higher than surrounding days
40% lower than surrounding days
About the same as surrounding days
About the same as surrounding days
About the same as surrounding days
About the same as surrounding days
About the same as surrounding days
151% higher than surrounding days
Grand Rapids-Wyoming, MI
Monitor comparison window 2025-07-28 to 2025-08-03 · PM2.5 target: GR-MONROE
171% above nearby days
58% higher than surrounding days
144% higher than surrounding days
171% higher than surrounding days
144% higher than surrounding days
39% higher than surrounding days
37% lower than surrounding days
303% lower than surrounding days
About the same as surrounding days
About the same as surrounding days
About the same as surrounding days
About the same as surrounding days
58% higher than surrounding days
Milwaukee-Waukesha-West Allis, WI
Monitor comparison window 2025-07-28 to 2025-08-03 · PM2.5 target: MILWAUKEE - SIXTEENTH ST. HEALTH CENTER
125% above nearby days
146% higher than surrounding days
120% higher than surrounding days
125% higher than surrounding days
120% higher than surrounding days
48% higher than surrounding days
22% lower than surrounding days
12% lower than surrounding days
13% lower than surrounding days
About the same as surrounding days
About the same as surrounding days
146% higher than surrounding days
Minneapolis-St. Paul-Bloomington, MN-WI
Monitor comparison window 2025-07-27 to 2025-08-04 · PM2.5 target: East Phillips Community
135% above nearby days
18% lower than surrounding days
62% higher than surrounding days
135% higher than surrounding days
62% higher than surrounding days
37% higher than surrounding days
15% lower than surrounding days
About the same as surrounding days
About the same as surrounding days
About the same as surrounding days
18% lower than surrounding days
Madison, WI
Monitor comparison window 2025-07-28 to 2025-08-03 · PM2.5 target: MADISON - UNIVERSITY AVE WELL #6
140% above nearby days
62% higher than surrounding days
120% higher than surrounding days
140% higher than surrounding days
120% higher than surrounding days
About the same as surrounding days
About the same as surrounding days
62% higher than surrounding days
Des Moines-West Des Moines, IA
Monitor comparison window 2025-07-28 to 2025-08-05 · PM2.5 target: CARPENTER
162% above nearby days
10% higher than surrounding days
56% higher than surrounding days
162% higher than surrounding days
56% higher than surrounding days
10% lower than surrounding days
About the same as surrounding days
About the same as surrounding days
10% higher than surrounding days
Kansas City, MO-KS
Monitor comparison window 2025-07-28 to 2025-08-05 · PM2.5 target: HERITAGE PARK
204% above nearby days
14% higher than surrounding days
79% higher than surrounding days
204% higher than surrounding days
79% higher than surrounding days
26% higher than surrounding days
13% lower than surrounding days
32% lower than surrounding days
About the same as surrounding days
About the same as surrounding days
About the same as surrounding days
About the same as surrounding days
14% higher than surrounding days
Omaha-Council Bluffs, NE-IA
Monitor comparison window 2025-07-28 to 2025-08-05 · PM2.5 target: 4102 Woolworth Ave. on Healthcenter Warehouse
198% above nearby days
About the same as surrounding days
72% higher than surrounding days
198% higher than surrounding days
72% higher than surrounding days
47% higher than surrounding days
43% lower than surrounding days
About the same as surrounding days
About the same as surrounding days
About the same as surrounding days
About the same as surrounding days
About the same as surrounding days
Detroit-Warren-Dearborn, MI
Monitor comparison window 2025-08-01 to 2025-08-07 · PM2.5 target: Port Huron
124% above nearby days
7% lower than surrounding days
78% higher than surrounding days
124% higher than surrounding days
78% higher than surrounding days
27% higher than surrounding days
33% higher than surrounding days
18% lower than surrounding days
10% higher than surrounding days
6% higher than surrounding days
About the same as surrounding days
About the same as surrounding days
7% lower than surrounding days
St. Louis, MO-IL
Monitor comparison window 2025-07-29 to 2025-08-04 · PM2.5 target: Branch Street
438% above nearby days
76% higher than surrounding days
214% higher than surrounding days
438% higher than surrounding days
214% higher than surrounding days
68% higher than surrounding days
About the same as surrounding days
About the same as surrounding days
About the same as surrounding days
12% lower than surrounding days
About the same as surrounding days
About the same as surrounding days
76% higher than surrounding days
Wichita, KS
Monitor comparison window 2025-07-29 to 2025-08-05 · PM2.5 target: PECK
166% above nearby days
50% higher than surrounding days
166% higher than surrounding days
50% higher than surrounding days
15% lower than surrounding days
112% lower than surrounding days
About the same as 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 |
|---|---|---|---|---|
| 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.
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.
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.
AQS PM2.5 qualifier IF — Fire - Canadian.
EPA AQS carries an agency-submitted informational qualifier (IF, Fire - Canadian.) on 168 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 24 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 24 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 96 PM2.5 samples in the candidate CBSA on 2025-08-03, 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 97 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 95 PM2.5 samples in the candidate CBSA on 2025-08-05, 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.
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.
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.
Agency determination A government body issued a record naming this cause for this event: an NWS air-quality alert, a NOAA Storm Events record, or a state or local official archive.
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.