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Wildfire smoke Agency determination provisional

July 15–20, 2026 Great Lakes and eastern U.S. wildfire-smoke episode

July 15, 2026 to July 20, 2026 · Origin: Canada; Northern Minnesota

Daily PM2.5 peaked at 387.8 µg/m³ near Toledo across 32 covered metros home to 86 million people. 14 metros recorded their worst day on record; 27 placed a top-ten day.

Counting the extra PM2.5 above each metro's typical day, this event handed the average affected resident ≈ 13.0 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 1.1 billion 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 basis for “Wildfire smoke”

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 17, 2026 official

AQS PM2.5 qualifier IF — Fire - Canadian.

EPA AQS carries an agency-submitted informational qualifier (IF, Fire - Canadian.) on 4 PM2.5 samples in the candidate CBSA on 2026-07-17, 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.

Michigan Department of Environment, Great Lakes, and Energy · Jul 16, 2026 official

Michigan fine-particle alert due to wildfire smoke

Michigan EGLE's July 16 update kept a PM2.5 alert in effect through July 17 and explicitly attributed the fine particles to wildfire smoke; this directly covers Detroit. IEM is the archive, not the official system of record.

Michigan Department of Environment, Great Lakes, and Energy · Jul 16, 2026 official

Michigan PM2.5 alert due to wildfire smoke

Michigan EGLE issued a July 16-17 fine-particle alert explicitly due to wildfire smoke, directly covering Grand Rapids. IEM is the archive, not the official system of record.

See every retained source and limitation ↓

Sequence: Detroit (Jul 15) → Milwaukee (Jul 15) → Minneapolis (Jul 15) → New York (Jul 15) → Rochester (Jul 15) → Toledo (Jul 16) → Chicago (Jul 16) → Grand Rapids (Jul 16) → Cleveland (Jul 16) → Columbus (Jul 16) → +22 more metros

Evidence path

From source to city

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.

Open the evidence ledger ↓
  1. 1

    Source or mechanism

    Wildfire smoke

    EPA AQS carries an agency-submitted informational qualifier (IF, Fire - Canadian.) on 4 PM2.5 samples in the candidate CBSA on 2026-07-17, identifying wildfire smoke as affecting the samples. An informational qualifier is an official…

    View supporting source ↗
    Documented
  2. 2

    Air-mass movement

    Transport into the affected region is documented

    Contemporaneous reporting identified heavy smoke from fires primarily in Canada and northern Minnesota extending from the Great Lakes to the East Coast.

    View transport source ↗
    Documented
  3. 3

    Local response

    387.8 µg/m³ near Toledo

    EPA monitors recorded the event across 32 metros. The peak daily concentration is roughly 17.6 cigarette-equivalents at the outdoor daily rate.

    Inspect the pollutant and weather signals ↓
    Documented

Event autopsy

What the instruments saw

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.

Observed context · not attribution

Detroit-Warren-Dearborn, MI

Monitor comparison window 2026-07-12 to 2026-07-20

0 pollutant signals
No comparable co-pollutant or weather observations were available.

The PM2.5 event remains in the catalog, but the surrounding monitoring record cannot supply a defensible instrument fingerprint for this place and date.

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.

Measured daily PM2.5 at EPA monitors, as cigarette-equivalents
EPA monitors sit in metro areas, so the colour clusters there. Land between and beyond them is unmeasured, not clean: this map shows where IAQng has readings, not the extent of the smoke.
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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

Camera views near

Browse the camera map →

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.

Affected metros

MetroPeak PM2.5Cigarettes, whole eventPeak dayAll-time standing
Toledo, OH 387.8 µg/m³ 33.0 Jul 16, 2026 Worst day on record
Chicago-Naperville-Elgin, IL-IN-WI 330.9 µg/m³ 27.6 Jul 16, 2026 Worst day on record
Detroit-Warren-Dearborn, MI 320.6 µg/m³ 30.7 Jul 16, 2026 Worst day on record
Grand Rapids-Wyoming, MI 316.5 µg/m³ 28.8 Jul 16, 2026 Worst day on record
Milwaukee-Waukesha-West Allis, WI 282.3 µg/m³ 31.1 Jul 16, 2026 Worst day on record
Cleveland-Elyria, OH 224 µg/m³ 20.3 Jul 17, 2026 Worst day on record
Columbus, OH 197.2 µg/m³ 11.6 Jul 17, 2026 Worst day on record
Pittsburgh, PA 190.4 µg/m³ 15.8 Jul 17, 2026 Worst day on record
Madison, WI 187.7 µg/m³ 17.1 Jul 16, 2026 #2 of its top days
Minneapolis-St. Paul-Bloomington, MN-WI 175.6 µg/m³ 13.3 Jul 16, 2026 Worst day on record
Washington-Arlington-Alexandria, DC-VA-MD-WV 170.8 µg/m³ 10.4 Jul 17, 2026 Worst day on record
Philadelphia-Camden-Wilmington, PA-NJ-DE-MD 169.3 µg/m³ 17.6 Jul 17, 2026 #3 of its top days
Akron, OH 164.2 µg/m³ 14.2 Jul 17, 2026 Worst day on record
Harrisburg-Carlisle, PA 148.8 µg/m³ 15.7 Jul 17, 2026 #3 of its top days
Allentown-Bethlehem-Easton, PA-NJ 132 µg/m³ 12.5 Jul 16, 2026 #2 of its top days
Buffalo-Cheektowaga-Niagara Falls, NY 131 µg/m³ 12.2 Jul 16, 2026 Worst day on record
Baltimore-Columbia-Towson, MD 114.7 µg/m³ 7.5 Jul 17, 2026 #2 of its top days
New York-Newark-Jersey City, NY-NJ-PA 109.8 µg/m³ 13.3 Jul 16, 2026 #3 of its top days
Richmond, VA 109.6 µg/m³ 5.0 Jul 17, 2026 Worst day on record
Rochester, NY 103.4 µg/m³ 8.6 Jul 16, 2026 Worst day on record
Dayton, OH 99.3 µg/m³ 4.5 Jul 17, 2026 #2 of its top days
Scranton--Wilkes-Barre--Hazleton, PA 80.4 µg/m³ 3.7 Jul 16, 2026 #6 of its top days
Syracuse, NY 78.9 µg/m³ 3.6 Jul 16, 2026 #4 of its top days
Virginia Beach-Norfolk-Newport News, VA-NC 71 µg/m³ 3.2 Jul 17, 2026 #5 of its top days
Bridgeport-Stamford-Norwalk, CT 69.5 µg/m³ 5.8 Jul 16, 2026 #5 of its top days
New Haven-Milford, CT 64.9 µg/m³ 5.3 Jul 16, 2026 #5 of its top days
Hartford-West Hartford-East Hartford, CT 53.4 µg/m³ 4.8 Jul 18, 2026 #6 of its top days
Indianapolis-Carmel-Anderson, IN 52.2 µg/m³ 2.4 Jul 19, 2026 #17 of its top days
Springfield, MA 48.1 µg/m³ 2.2 Jul 18, 2026 #15 of its top days
Boston-Cambridge-Newton, MA-NH 43.8 µg/m³ 2.0 Jul 18, 2026 #20 of its top days
Albany-Schenectady-Troy, NY 42.6 µg/m³ 1.9 Jul 16, 2026 #19 of its top days
Worcester, MA-CT 41.6 µg/m³ 1.9 Jul 18, 2026 #12 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

What supports this account

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.

EPA AQS monitor qualifier 1

  • AQS PM2.5 qualifier IF — Fire - Canadian.

    U.S. EPA Air Quality System and the submitting air monitoring agency · Jul 17, 2026 official government

    EPA AQS carries an agency-submitted informational qualifier (IF, Fire - Canadian.) on 4 PM2.5 samples in the candidate CBSA on 2026-07-17, 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 6

  • Michigan fine-particle alert due to wildfire smoke

    Michigan Department of Environment, Great Lakes, and Energy · Jul 16, 2026 official government

    Michigan EGLE's July 16 update kept a PM2.5 alert in effect through July 17 and explicitly attributed the fine particles to wildfire smoke; this directly covers Detroit. IEM is the archive, not the official system of record.

  • Michigan PM2.5 alert due to wildfire smoke

    Michigan Department of Environment, Great Lakes, and Energy · Jul 16, 2026 official government

    Michigan EGLE issued a July 16-17 fine-particle alert explicitly due to wildfire smoke, directly covering Grand Rapids. IEM is the archive, not the official system of record.

  • Illinois Air Quality Action Day for wildfire smoke and PM2.5

    Illinois Environmental Protection Agency · Jul 17, 2026 official government

    Illinois EPA issued a July 17 Air Quality Action Day explicitly for wildfire smoke and PM2.5, directly covering Chicago. IEM is the archive, not the official system of record.

  • West Virginia fine-particle alert due to wildfire smoke

    West Virginia Department of Environmental Protection · Jul 17, 2026 official government

    West Virginia's alert attributed unhealthy to very unhealthy fine-particle concentrations during July 17-18 to wildfire smoke. It supports only the West Virginia portion of the Washington regional metro candidate. IEM is the archive, not the official system of record.

  • Indiana PM2.5 alert for wildfire smoke

    Indiana Department of Environmental Management · Jul 19, 2026 official government

    Indiana's July 19 alert tied observed and forecast high PM2.5 to wildfire-smoke exposure and applied to Indianapolis. IEM is the archive, not the official system of record.

  • Illinois PM2.5 alert for wildfire smoke

    Illinois Environmental Protection Agency · Jul 19, 2026 official government

    Illinois EPA's July 19 alert linked observed and forecast elevated PM2.5 to wildfire smoke, directly covering Chicago. IEM is the archive, not the official system of record.

Agency and publisher pages 6

gdelt-doc-api 1

What remains uncertain

Status and provenance

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. Recent days are preliminary AirNow readings and re-rank once EPA certifies them. 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.