SmogRank / Episodes / United States

North-eastern United States, January 2025

For 1 day, on 10 January 2025, 9 cities in the United States and Canada had PM2.5 at least twice their usual for the time of year. The worst reading was Oconomowoc, Wisconsin, United States: 40.0 µg/m³ on 10 January, about 6.7× its usual 6.0.

No cause namedWe have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached9in 2 countries
Days110 January 2025
Worst day10 January9 cities counted
Furthest above usual6.7×Oconomowoc

Day by day

10 January 9 cities at twice their usual or more
PerrysburgLimaYpsilantiFort WayneTaylorLincoln ParkDearbornLansingSouthfieldDetroitSpringfieldEastpointeFlintDaytonMuncieElkhartWestervilleColumbusGahannaMiddletownLebanonAndersonSouth BendMasonWyomingGrand RapidsKokomoBay CityJenisonChathamWhite OakNorwoodPort HuronCincinnatiMedinaHollandSarniaFishersFort ThomasClevelandCleveland HeightsShaker HeightsAkronMichigan CityColumbusCantonLafayettePainesvillePortageGaryBloomingtonEast ChicagoSt. ThomasHammondLondonCalumet CityWarrenChicagoYoungstownElmwood ParkBrookfieldSteubenvilleNorthbrookFranklin ParkWheelingWeirtonHermitageDes PlainesTerre HauteZionWeirton HeightsJolietSouth MilwaukeeNapervilleMilwaukeeCaryElginAuroraErieKitchenerBrantfordChampaignPittsburghWaukeshaWilkinsburgMcKeesportGuelphHamiltonWaterdownMiltonBloomingtonOakvilleBramptonRockfordMississaugaDecaturSt. CatharinesTorontoJohnstownPeoriaMadisonBuffaloKenmoreRedfordWindsorIndianapolisDublinKalamazooToledoWest MifflinOregonOconomowoc
7 Jan8910111213
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

OconomowocOconomowoc, 7 January: 3.5 µg/m³, 0.6× usualOconomowoc, 8 January: 6.1 µg/m³, 1.0× usualOconomowoc, 9 January: 18.5 µg/m³, 3.1× usualOconomowoc, 10 January: 40.0 µg/m³, 6.7× usualOconomowoc, 11 January: no readingOconomowoc, 12 January: no readingOconomowoc, 13 January: no readingRedfordRedford, 7 January: 5.5 µg/m³, 0.4× usualRedford, 8 January: 6.3 µg/m³, 0.5× usualRedford, 9 January: 10.4 µg/m³, 0.8× usualRedford, 10 January: 29.0 µg/m³, 2.2× usualRedford, 11 January: 20.4 µg/m³, 1.5× usualRedford, 12 January: 20.1 µg/m³, 1.5× usualRedford, 13 January: 13.9 µg/m³, 1.0× usualOregonOregon, 7 January: 4.8 µg/m³, 0.6× usualOregon, 8 January: 5.5 µg/m³, 0.7× usualOregon, 9 January: 11.5 µg/m³, 1.5× usualOregon, 10 January: 28.0 µg/m³, 3.6× usualOregon, 11 January: 20.0 µg/m³, 2.6× usualOregon, 12 January: 17.6 µg/m³, 2.3× usualOregon, 13 January: 8.9 µg/m³, 1.2× usualWest MifflinWest Mifflin, 7 January: 4.1 µg/m³, 0.5× usualWest Mifflin, 8 January: 5.5 µg/m³, 0.7× usualWest Mifflin, 9 January: 6.7 µg/m³, 0.9× usualWest Mifflin, 10 January: 27.6 µg/m³, 3.6× usualWest Mifflin, 11 January: 21.8 µg/m³, 2.9× usualWest Mifflin, 12 January: 19.7 µg/m³, 2.6× usualWest Mifflin, 13 January: 7.3 µg/m³, 1.0× usualToledoToledo, 7 January: 4.3 µg/m³, 0.5× usualToledo, 8 January: 4.2 µg/m³, 0.5× usualToledo, 9 January: 10.1 µg/m³, 1.3× usualToledo, 10 January: 27.1 µg/m³, 3.4× usualToledo, 11 January: 21.4 µg/m³, 2.7× usualToledo, 12 January: 17.7 µg/m³, 2.2× usualToledo, 13 January: 8.5 µg/m³, 1.1× usualKalamazooKalamazoo, 7 January: 2.5 µg/m³, 0.3× usualKalamazoo, 8 January: 4.0 µg/m³, 0.5× usualKalamazoo, 9 January: 6.4 µg/m³, 0.8× usualKalamazoo, 10 January: 27.1 µg/m³, 3.3× usualKalamazoo, 11 January: 12.7 µg/m³, 1.6× usualKalamazoo, 12 January: 13.9 µg/m³, 1.7× usualKalamazoo, 13 January: 4.8 µg/m³, 0.6× usualIndianapolisIndianapolis, 7 January: 5.6 µg/m³, 0.6× usualIndianapolis, 8 January: 11.4 µg/m³, 1.3× usualIndianapolis, 9 January: 22.7 µg/m³, 2.5× usualIndianapolis, 10 January: 26.7 µg/m³, 3.0× usualIndianapolis, 11 January: 14.9 µg/m³, 1.7× usualIndianapolis, 12 January: 13.4 µg/m³, 1.5× usualIndianapolis, 13 January: 5.3 µg/m³, 0.6× usualWindsorWindsor, 7 January: 3.2 µg/m³, 0.4× usualWindsor, 8 January: 3.7 µg/m³, 0.4× usualWindsor, 9 January: 7.2 µg/m³, 0.8× usualWindsor, 10 January: 26.0 µg/m³, 2.9× usualWindsor, 11 January: 19.9 µg/m³, 2.2× usualWindsor, 12 January: 17.0 µg/m³, 1.9× usualWindsor, 13 January: 10.1 µg/m³, 1.1× usualDublinDublin, 7 January: 5.2 µg/m³, 0.7× usualDublin, 8 January: 11.4 µg/m³, 1.4× usualDublin, 9 January: 15.5 µg/m³, 2.0× usualDublin, 10 January: 25.4 µg/m³, 3.2× usualDublin, 11 January: 18.0 µg/m³, 2.3× usualDublin, 12 January: 16.0 µg/m³, 2.0× usualDublin, 13 January: 7.2 µg/m³, 0.9× usual7 Jan8910111213
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 40.010 January6.06.7×
OregonOhio, United States1 28.010 January7.73.6×
West MifflinPennsylvania, United States1 27.610 January7.63.6×
ToledoOhio, United States1 27.110 January8.03.4×
KalamazooMichigan, United States1 27.110 January8.13.3×
DublinOhio, United States1 25.410 January7.93.2×
IndianapolisIndiana, United States1 26.710 January9.03.0×
WindsorOntario, Canada1 26.010 January9.02.9×
RedfordMichigan, United States1 29.010 January13.42.2×

Daily means in µg/m³. Usual: the city's median for this time of year (its days within 21 days of the date, every year, leaving out the week around it). Above usual: its highest day against that.

Against other episodes in the United States and Canada

Number 85 of 106 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 106.

Use this page

SmogRank, North-eastern United States, January 2025: 9 cities with PM2.5 at twice their usual or more, 10 January 2025, smogrank.com/episodes/2025-01-north-eastern-united-states (accessed 2 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.