SmogRank / Episodes / United States

North-eastern United States and Canada, 9 to 10 February 2026

For 2 days, from 9 to 10 February 2026, 10 cities in the United States and Canada had PM2.5 at least twice their usual for the time of year. The worst reading was Ann Arbor, Michigan, United States: 29.9 µg/m³ on 10 February, about 4.7× its usual 6.4. Ended 10 February.

No cause namedWe have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached10in 2 countries
Days29 to 10 February 2026
Worst day10 February6 cities counted
Furthest above usual5.1×Oconomowoc

Day by day

10 February 6 cities at twice their usual or more
Fort WayneColumbia CityMuncieAndersonLimaKokomoElkhartMcCordsvilleFishersSouth BendKalamazooDaytonIndianapolisMiddletownMaumeeTecumsehPerrysburgSpringfieldToledoLebanonMasonOregonWhite OakSharonvilleDentLafayetteNorwoodCincinnatiLansingColumbusFort ThomasMichigan CityYpsilantiHighland HeightsWyomingHudsonvilleJenisonGrand RapidsHollandDublinPortageTaylorBloomingtonColumbusRedfordLincoln ParkGaryDearbornGahannaSouthfieldNew AlbanyEast ChicagoDetroitHammondCalumet CityDoltonEastpointeBlue IslandChicagoEvergreen ParkTerre HauteOak LawnEvanstonBridgeviewLincolnwoodSkokieElmwood ParkBrookfieldNilesNew BaltimoreFranklin ParkPark RidgeNorthbrookDes PlainesJolietJasperZionBraidwoodWinthrop HarborNapervilleWarrenvilleMedinaChampaignSavoyChathamAuroraPort HuronElginFlatwoodsSarniaCaryAshlandMilwaukeeAkronCleveland HeightsWarrensville HeightsShaker HeightsHuntingtonCantonWaukeshaBloomingtonPainesvilleDecaturRockfordWarrenSt. ThomasLondonYoungstownMoundsvilleSteubenvillePeoriaWeirtonWeirton HeightsHermitageSpringfieldBeaver FallsNew BrightonMadisonMiddletonCanonsburgKennedy TownshipBridgevilleUpper Saint ClairPittsburghErieClintonJefferson HillsKitchenerWilkinsburgWest MifflinMcKeesportMonessenBarabooBrantfordNatrona HeightsWood RiverUpper AltonUniontownGranite CityJerseyvilleEast Saint LouisSt. LouisUniversity CityLemayHamiltonWaterdownArnoldClevelandWestervilleWindsorGreendaleSouth MilwaukeeWheelersburgPortsmouthWheatonAnn ArborOconomowoc
6 Feb78910111213
Every measured city in the area, coloured by its PM2.5 that day; a dark ring marks a city at twice its usual or more. Bars: cities counted each day, coloured by their median level. Choose a day or press play; without JavaScript, the days link to that day's world ranking.

How it spread

WheatonWheaton, 6 February: 16.7 µg/m³Wheaton, 7 February: 2.4 µg/m³Wheaton, 8 February: 14.9 µg/m³Wheaton, 9 February: 28.2 µg/m³, 4.2× its usual 6.7Wheaton, 10 February: 27.5 µg/m³Wheaton, 11 February: 9.2 µg/m³Wheaton, 12 February: 16.9 µg/m³Wheaton, 13 February: 19.1 µg/m³South MilwaukeeSouth Milwaukee, 6 February: 8.7 µg/m³South Milwaukee, 7 February: 5.0 µg/m³South Milwaukee, 8 February: 4.1 µg/m³South Milwaukee, 9 February: 26.5 µg/m³, 3.4× its usual 7.9South Milwaukee, 10 February: 13.9 µg/m³South Milwaukee, 11 February: 8.5 µg/m³South Milwaukee, 12 February: 7.4 µg/m³South Milwaukee, 13 February: 14.9 µg/m³GreendaleGreendale, 6 February: 8.7 µg/m³Greendale, 7 February: 5.0 µg/m³Greendale, 8 February: 4.1 µg/m³Greendale, 9 February: 26.5 µg/m³, 3.3× its usual 8.0Greendale, 10 February: 13.9 µg/m³Greendale, 11 February: 8.5 µg/m³Greendale, 12 February: 7.4 µg/m³Greendale, 13 February: 14.9 µg/m³OconomowocOconomowoc, 6 February: 8.1 µg/m³Oconomowoc, 7 February: 2.0 µg/m³Oconomowoc, 8 February: 3.8 µg/m³Oconomowoc, 9 February: 25.7 µg/m³, 5.1× its usual 4.4Oconomowoc, 10 February: 14.9 µg/m³Oconomowoc, 11 February: 4.3 µg/m³Oconomowoc, 12 February: 6.1 µg/m³Oconomowoc, 13 February: 22.3 µg/m³Ann ArborAnn Arbor, 6 February: 21.1 µg/m³Ann Arbor, 7 February: 4.0 µg/m³Ann Arbor, 8 February: no readingAnn Arbor, 9 February: 11.7 µg/m³Ann Arbor, 10 February: 29.9 µg/m³, 4.7× its usual 6.4Ann Arbor, 11 February: 6.8 µg/m³Ann Arbor, 12 February: 6.6 µg/m³Ann Arbor, 13 February: 16.9 µg/m³PortsmouthPortsmouth, 6 February: 31.0 µg/m³Portsmouth, 7 February: 4.0 µg/m³Portsmouth, 8 February: 12.2 µg/m³Portsmouth, 9 February: 11.7 µg/m³Portsmouth, 10 February: 27.8 µg/m³, 3.6× its usual 7.8Portsmouth, 11 February: 21.7 µg/m³Portsmouth, 12 February: 13.4 µg/m³Portsmouth, 13 February: 21.2 µg/m³WheelersburgWheelersburg, 6 February: 31.0 µg/m³Wheelersburg, 7 February: 4.0 µg/m³Wheelersburg, 8 February: 12.2 µg/m³Wheelersburg, 9 February: 11.7 µg/m³Wheelersburg, 10 February: 27.8 µg/m³, 3.6× its usual 7.8Wheelersburg, 11 February: 21.7 µg/m³Wheelersburg, 12 February: 13.4 µg/m³Wheelersburg, 13 February: 21.2 µg/m³WindsorWindsor, 6 February: 20.4 µg/m³Windsor, 7 February: 4.4 µg/m³Windsor, 8 February: 5.6 µg/m³Windsor, 9 February: 14.0 µg/m³Windsor, 10 February: 27.4 µg/m³, 2.9× its usual 9.4Windsor, 11 February: 5.4 µg/m³Windsor, 12 February: 5.9 µg/m³Windsor, 13 February: 19.0 µg/m³WestervilleWesterville, 6 February: 24.1 µg/m³Westerville, 7 February: 5.0 µg/m³Westerville, 8 February: 14.6 µg/m³Westerville, 9 February: 12.2 µg/m³Westerville, 10 February: 25.2 µg/m³, 2.8× its usual 9.0Westerville, 11 February: 9.9 µg/m³Westerville, 12 February: 12.1 µg/m³Westerville, 13 February: 23.3 µg/m³ClevelandCleveland, 6 February: 23.4 µg/m³Cleveland, 7 February: 3.7 µg/m³Cleveland, 8 February: 7.5 µg/m³Cleveland, 9 February: 11.7 µg/m³Cleveland, 10 February: 25.0 µg/m³, 2.7× its usual 9.3Cleveland, 11 February: 7.1 µg/m³Cleveland, 12 February: 6.6 µg/m³Cleveland, 13 February: 15.3 µg/m³6 Feb78910111213
Every counted city, in the order the episode reached them, 3 days before to 3 after. Each square is a day, coloured by that day's PM2.5; outlined: at twice the city's usual or more.
Good0–50
Moderate51–100
Sensitive groups101–150
Unhealthy151–200
Very unhealthy201–300
Hazardous301+

Every city it reached

CityDaysHighestUsualAbove usual
OconomowocWisconsin, United States1 25.79 February4.45.1×
Ann ArborMichigan, United States1 29.910 February6.44.7×
WheatonIllinois, United States1 28.29 February6.74.2×
PortsmouthOhio, United States1 27.810 February7.83.6×
WheelersburgOhio, United States1 27.810 February7.83.6×
South MilwaukeeWisconsin, United States1 26.59 February7.93.4×
GreendaleWisconsin, United States1 26.59 February8.03.3×
WindsorOntario, Canada1 27.410 February9.42.9×
WestervilleOhio, United States1 25.210 February9.02.8×
ClevelandOhio, United States1 25.010 February9.32.7×

Daily means in µg/m³, over the days each city counted in this episode. Highest: its highest of those days. Usual: the city's median for the time of year of that day (its days within 21 days of the date, every year, leaving out the week around it). Above usual: its highest day against that, with a usual under 5 µg/m³ taken as 5.

Against other episodes in the United States and Canada

Number 136 of 173 episodes in the United States and Canada since our records began, by cities reached.

Bars: cities reached; colour: the level of the episode's highest daily reading. All 173.

Use this page

SmogRank, North-eastern United States and Canada, 9 to 10 February 2026: 10 cities with PM2.5 at twice their usual or more, 9 to 10 February 2026, smogrank.com/episodes/2026-02-09-north-eastern-united-states-and-canada (accessed 5 October 2026).

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You're welcome to reuse a single chart, image or figure with this citation and a link. Terms.

An episode is a run of days when many cities close to each other (four or more within 350 km on a day, 8 or more in all) each had a daily PM2.5 mean of at least 25 µg/m³ and at least 2 times their usual for that time of year. Found in our own measurements, not picked by hand. How we find episodes. Values are each city's daily mean of its own monitors; causes are the usual kinds for a pattern like this, not a confirmed source.