SmogRank / Episodes / United States

Northern United States and Canada, May 2024

For 3 days, from 12 to 14 May 2024, 25 cities in the United States and Canada had PM2.5 at least twice their usual for the time of year. The worst reading was Rochester, Minnesota, United States: 61.8 µg/m³ on 13 May, about 10× its usual 5.9.

No cause namedWe have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached25in 2 countries
Days312 to 14 May 2024
Worst day13 May15 cities counted
Furthest above usual11×Eau Claire

Day by day

13 May 15 cities at twice their usual or more
AnkenyDes MoinesIowa CityMuscatineDavenportMolineClintonMadisonSaint JosephRockfordPeoriaColumbiaLibertyKansas CitySpringfieldRaymoreBloomingtonSioux FallsOlatheLincolnUpper AltonCaryWaukeshaUniversity CityNapervilleDecaturGranite CitySt. LouisEast Saint LouisLemayJolietArnoldMilwaukeeDes PlainesSouth MilwaukeeZionFranklin ParkNorthbrookBrookfieldOak LawnChampaignChicagoCalumet CityHammondEast ChicagoSpringfieldGaryPortageTerre HauteSpringdaleMarquettePaducahEvansvilleTulsaDyersburgJenksClarksvilleWaterlooKansas CityOmahaDerbyBrookingsWatertownPonca CityBellevueGreen BayAppletonSuperiorTopekaSaint CloudDuluthWest FargoThunder BaySaint MichaelSaint PaulMinneapolisShakopeeBlaineApple ValleyRochesterBurnsvilleEau Claire
9 May1011121314151617
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

West FargoWest Fargo, 9 May: 4.0 µg/m³West Fargo, 10 May: 5.9 µg/m³West Fargo, 11 May: 9.7 µg/m³West Fargo, 12 May: 48.1 µg/m³, 8.0× its usual 6.0West Fargo, 13 May: 14.3 µg/m³West Fargo, 14 May: 11.0 µg/m³West Fargo, 15 May: 5.0 µg/m³West Fargo, 16 May: no readingWest Fargo, 17 May: no readingThunder BayThunder Bay, 9 May: 3.0 µg/m³Thunder Bay, 10 May: 4.9 µg/m³Thunder Bay, 11 May: 3.3 µg/m³Thunder Bay, 12 May: 40.7 µg/m³, 8.1× its usual 3.8Thunder Bay, 13 May: 10.9 µg/m³Thunder Bay, 14 May: 2.9 µg/m³Thunder Bay, 15 May: 5.8 µg/m³Thunder Bay, 16 May: 5.0 µg/m³Thunder Bay, 17 May: 3.5 µg/m³DuluthDuluth, 9 May: 1.5 µg/m³Duluth, 10 May: 2.8 µg/m³Duluth, 11 May: 3.7 µg/m³Duluth, 12 May: 37.2 µg/m³, 7.4× its usual 4.0Duluth, 13 May: 19.8 µg/m³Duluth, 14 May: 2.0 µg/m³Duluth, 15 May: 1.8 µg/m³Duluth, 16 May: 4.8 µg/m³Duluth, 17 May: 4.5 µg/m³SuperiorSuperior, 9 May: 1.6 µg/m³Superior, 10 May: 2.8 µg/m³Superior, 11 May: 4.1 µg/m³Superior, 12 May: 36.2 µg/m³, 7.2× its usual 4.6Superior, 13 May: 21.7 µg/m³Superior, 14 May: 2.9 µg/m³Superior, 15 May: 2.2 µg/m³Superior, 16 May: 4.4 µg/m³Superior, 17 May: 5.2 µg/m³Saint MichaelSaint Michael, 9 May: 2.1 µg/m³Saint Michael, 10 May: 4.7 µg/m³Saint Michael, 11 May: 6.1 µg/m³Saint Michael, 12 May: 33.8 µg/m³, 6.8× its usual 4.9Saint Michael, 13 May: 42.0 µg/m³, 8.4× its usual 5.0Saint Michael, 14 May: 9.9 µg/m³Saint Michael, 15 May: 11.3 µg/m³Saint Michael, 16 May: 7.5 µg/m³Saint Michael, 17 May: 9.2 µg/m³Saint CloudSaint Cloud, 9 May: 1.7 µg/m³Saint Cloud, 10 May: 4.1 µg/m³Saint Cloud, 11 May: 5.3 µg/m³Saint Cloud, 12 May: 29.0 µg/m³, 5.7× its usual 5.1Saint Cloud, 13 May: 37.1 µg/m³, 7.3× its usual 5.1Saint Cloud, 14 May: 8.2 µg/m³Saint Cloud, 15 May: 10.1 µg/m³Saint Cloud, 16 May: 6.5 µg/m³Saint Cloud, 17 May: 8.4 µg/m³WatertownWatertown, 9 May: 4.3 µg/m³Watertown, 10 May: 7.0 µg/m³Watertown, 11 May: 7.2 µg/m³Watertown, 12 May: 26.0 µg/m³, 3.9× its usual 6.7Watertown, 13 May: 33.7 µg/m³, 5.0× its usual 6.7Watertown, 14 May: 14.3 µg/m³Watertown, 15 May: 15.6 µg/m³Watertown, 16 May: 13.3 µg/m³Watertown, 17 May: 9.7 µg/m³BlaineBlaine, 9 May: 2.4 µg/m³Blaine, 10 May: 4.0 µg/m³Blaine, 11 May: 6.1 µg/m³Blaine, 12 May: 25.8 µg/m³, 5.2× its usual 4.8Blaine, 13 May: 48.1 µg/m³, 9.6× its usual 4.8Blaine, 14 May: 9.1 µg/m³Blaine, 15 May: 11.0 µg/m³Blaine, 16 May: 9.3 µg/m³Blaine, 17 May: 8.8 µg/m³Saint PaulSaint Paul, 9 May: no readingSaint Paul, 10 May: 4.3 µg/m³Saint Paul, 11 May: 6.3 µg/m³Saint Paul, 12 May: 25.0 µg/m³, 4.4× its usual 5.7Saint Paul, 13 May: 49.2 µg/m³, 8.6× its usual 5.7Saint Paul, 14 May: 11.4 µg/m³Saint Paul, 15 May: 10.1 µg/m³Saint Paul, 16 May: 11.2 µg/m³Saint Paul, 17 May: 8.9 µg/m³RochesterRochester, 9 May: 3.5 µg/m³Rochester, 10 May: 4.6 µg/m³Rochester, 11 May: 8.9 µg/m³Rochester, 12 May: 7.3 µg/m³Rochester, 13 May: 61.8 µg/m³, 10× its usual 5.9Rochester, 14 May: 22.0 µg/m³Rochester, 15 May: 17.2 µg/m³Rochester, 16 May: 12.6 µg/m³Rochester, 17 May: 12.7 µg/m³BurnsvilleBurnsville, 9 May: 3.4 µg/m³Burnsville, 10 May: 4.4 µg/m³Burnsville, 11 May: 7.8 µg/m³Burnsville, 12 May: 21.2 µg/m³Burnsville, 13 May: 59.6 µg/m³, 11× its usual 5.5Burnsville, 14 May: 16.2 µg/m³Burnsville, 15 May: 14.4 µg/m³Burnsville, 16 May: 12.2 µg/m³Burnsville, 17 May: no readingEau ClaireEau Claire, 9 May: 2.7 µg/m³Eau Claire, 10 May: 2.9 µg/m³Eau Claire, 11 May: 4.3 µg/m³Eau Claire, 12 May: 11.1 µg/m³Eau Claire, 13 May: 56.0 µg/m³, 11× its usual 5.1Eau Claire, 14 May: 15.4 µg/m³Eau Claire, 15 May: 6.8 µg/m³Eau Claire, 16 May: 9.2 µg/m³Eau Claire, 17 May: 9.5 µg/m³ShakopeeShakopee, 9 May: 2.7 µg/m³Shakopee, 10 May: 4.3 µg/m³Shakopee, 11 May: 6.0 µg/m³Shakopee, 12 May: 24.7 µg/m³Shakopee, 13 May: 53.7 µg/m³, 9.0× its usual 6.0Shakopee, 14 May: 15.1 µg/m³Shakopee, 15 May: 13.3 µg/m³Shakopee, 16 May: 9.6 µg/m³Shakopee, 17 May: 9.1 µg/m³Apple ValleyApple Valley, 9 May: 3.0 µg/m³Apple Valley, 10 May: 3.7 µg/m³Apple Valley, 11 May: 5.4 µg/m³Apple Valley, 12 May: 18.5 µg/m³Apple Valley, 13 May: 53.5 µg/m³, 9.9× its usual 5.4Apple Valley, 14 May: 15.1 µg/m³Apple Valley, 15 May: 14.1 µg/m³Apple Valley, 16 May: 10.2 µg/m³Apple Valley, 17 May: 11.6 µg/m³MinneapolisMinneapolis, 9 May: 3.0 µg/m³Minneapolis, 10 May: 5.2 µg/m³Minneapolis, 11 May: 6.1 µg/m³Minneapolis, 12 May: 22.9 µg/m³Minneapolis, 13 May: 51.2 µg/m³, 8.8× its usual 5.8Minneapolis, 14 May: 11.2 µg/m³Minneapolis, 15 May: 12.4 µg/m³Minneapolis, 16 May: 9.9 µg/m³Minneapolis, 17 May: 9.4 µg/m³AppletonAppleton, 9 May: 3.1 µg/m³Appleton, 10 May: 2.2 µg/m³Appleton, 11 May: 2.8 µg/m³Appleton, 12 May: 5.3 µg/m³Appleton, 13 May: 33.9 µg/m³, 6.8× its usual 4.7Appleton, 14 May: 1.7 µg/m³Appleton, 15 May: 4.4 µg/m³Appleton, 16 May: 9.7 µg/m³Appleton, 17 May: 7.1 µg/m³BrookingsBrookings, 9 May: 2.4 µg/m³Brookings, 10 May: 6.5 µg/m³Brookings, 11 May: 7.7 µg/m³Brookings, 12 May: 19.0 µg/m³Brookings, 13 May: 33.5 µg/m³, 4.7× its usual 7.1Brookings, 14 May: 10.9 µg/m³Brookings, 15 May: 14.1 µg/m³Brookings, 16 May: 11.3 µg/m³Brookings, 17 May: 10.0 µg/m³Green BayGreen Bay, 9 May: 2.6 µg/m³Green Bay, 10 May: 2.4 µg/m³Green Bay, 11 May: 2.6 µg/m³Green Bay, 12 May: 4.7 µg/m³Green Bay, 13 May: 28.1 µg/m³, 5.6× its usual 4.8Green Bay, 14 May: 1.5 µg/m³Green Bay, 15 May: 3.2 µg/m³Green Bay, 16 May: 9.1 µg/m³Green Bay, 17 May: 6.7 µg/m³WaterlooWaterloo, 9 May: 4.9 µg/m³Waterloo, 10 May: 4.9 µg/m³Waterloo, 11 May: 8.1 µg/m³Waterloo, 12 May: 7.3 µg/m³Waterloo, 13 May: 25.4 µg/m³, 3.0× its usual 8.6Waterloo, 14 May: 21.2 µg/m³Waterloo, 15 May: 16.5 µg/m³Waterloo, 16 May: 7.8 µg/m³Waterloo, 17 May: 10.5 µg/m³TopekaTopeka, 9 May: 3.3 µg/m³Topeka, 10 May: 4.6 µg/m³Topeka, 11 May: 5.8 µg/m³Topeka, 12 May: 6.4 µg/m³Topeka, 13 May: 9.2 µg/m³Topeka, 14 May: 46.3 µg/m³, 7.2× its usual 6.4Topeka, 15 May: 16.9 µg/m³Topeka, 16 May: 9.3 µg/m³Topeka, 17 May: 8.1 µg/m³Ponca CityPonca City, 9 May: no readingPonca City, 10 May: 5.4 µg/m³Ponca City, 11 May: 7.4 µg/m³Ponca City, 12 May: 10.2 µg/m³Ponca City, 13 May: 5.1 µg/m³Ponca City, 14 May: 35.5 µg/m³, 5.4× its usual 6.6Ponca City, 15 May: 30.1 µg/m³Ponca City, 16 May: 7.3 µg/m³Ponca City, 17 May: 11.4 µg/m³DerbyDerby, 9 May: 4.5 µg/m³Derby, 10 May: 7.4 µg/m³Derby, 11 May: 8.4 µg/m³Derby, 12 May: 5.1 µg/m³Derby, 13 May: 3.5 µg/m³Derby, 14 May: 31.8 µg/m³, 4.5× its usual 7.0Derby, 15 May: 21.4 µg/m³Derby, 16 May: 3.7 µg/m³Derby, 17 May: 5.8 µg/m³OmahaOmaha, 9 May: 3.4 µg/m³Omaha, 10 May: 4.3 µg/m³Omaha, 11 May: 7.7 µg/m³Omaha, 12 May: 6.4 µg/m³Omaha, 13 May: 16.3 µg/m³Omaha, 14 May: 27.9 µg/m³, 4.4× its usual 6.3Omaha, 15 May: 8.0 µg/m³Omaha, 16 May: 7.4 µg/m³Omaha, 17 May: 4.5 µg/m³BellevueBellevue, 9 May: 2.6 µg/m³Bellevue, 10 May: no readingBellevue, 11 May: 4.4 µg/m³Bellevue, 12 May: no readingBellevue, 13 May: 16.8 µg/m³Bellevue, 14 May: 27.6 µg/m³, 5.5× its usual 4.9Bellevue, 15 May: 4.7 µg/m³Bellevue, 16 May: 7.0 µg/m³Bellevue, 17 May: 4.3 µg/m³Kansas CityKansas City, 9 May: 3.1 µg/m³Kansas City, 10 May: 4.9 µg/m³Kansas City, 11 May: 8.5 µg/m³Kansas City, 12 May: 7.5 µg/m³Kansas City, 13 May: 6.6 µg/m³Kansas City, 14 May: 25.7 µg/m³, 3.8× its usual 6.7Kansas City, 15 May: 10.2 µg/m³Kansas City, 16 May: 8.8 µg/m³Kansas City, 17 May: 10.5 µg/m³9 May1011121314151617
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
Eau ClaireWisconsin, United States1 56.013 May5.111×
BurnsvilleMinnesota, United States1 59.613 May5.511×
RochesterMinnesota, United States1 61.813 May5.911×
Apple ValleyMinnesota, United States1 53.513 May5.49.9×
BlaineMinnesota, United States2 48.113 May4.89.6×
ShakopeeMinnesota, United States1 53.713 May6.09.0×
MinneapolisMinnesota, United States1 51.213 May5.88.8×
Saint PaulMinnesota, United States2 49.213 May5.78.6×
Saint MichaelMinnesota, United States2 42.013 May5.08.4×
Thunder BayOntario, Canada1 40.712 May3.88.1×
West FargoNorth Dakota, United States1 48.112 May6.08.0×
DuluthMinnesota, United States1 37.212 May4.07.4×
Saint CloudMinnesota, United States2 37.113 May5.17.3×
TopekaKansas, United States1 46.314 May6.47.2×
SuperiorWisconsin, United States1 36.212 May4.67.2×
AppletonWisconsin, United States1 33.913 May4.76.8×
Green BayWisconsin, United States1 28.113 May4.85.6×
BellevueNebraska, United States1 27.614 May4.95.5×
Ponca CityOklahoma, United States1 35.514 May6.65.4×
WatertownSouth Dakota, United States2 33.713 May6.75.0×
BrookingsSouth Dakota, United States1 33.513 May7.14.7×
DerbyKansas, United States1 31.814 May7.04.5×
OmahaNebraska, United States1 27.914 May6.34.4×
Kansas CityKansas, United States1 25.714 May6.73.8×
WaterlooIowa, United States1 25.413 May8.63.0×

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 39 of 141 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 141.

Use this page

SmogRank, Northern United States and Canada, May 2024: 25 cities with PM2.5 at twice their usual or more, 12 to 14 May 2024, smogrank.com/episodes/2024-05-northern-united-states-and-canada (accessed 4 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.