SmogRank / Episodes / United States
Southern United States, May 2023
For 4 days, from 21 to 24 May 2023, 21 cities in the United States had PM2.5 at least twice their usual for the time of year. The worst reading was Cleveland, Mississippi, United States: 32.7 µg/m³ on 22 May, about 4.8× its usual 6.8. Ended 24 May.
No cause named We have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached 21 in 1 country
Days 4 21 to 24 May 2023
Worst day 21 May 8 cities counted
Furthest above usual 4.8× Cleveland
Day by day
Play 21 May 8 cities at twice their usual or more
Gulfport Waveland Prichard Pascagoula West Memphis Bartlett Marion Baton Rouge New Orleans Fairhope Hueytown Fairfield Birmingham Jackson Trussville Ferry Pass Leeds Decatur Lafayette Little Rock Montgomery Dyersburg Midway Gadsden Columbia Shreveport Texarkana Phenix City Hendersonville Atlanta Fort Smith Cookeville Candler-McAfee McDonough Albany Springdale Athens Tallahassee Lawrenceville Macon Warner Robins Gainesville Harriman Loudon Athens McAlester Maryville Missouri City Valdosta Mission Bend College Station Jenks Glenpool Tulsa Houston Highlands Baytown Conroe Pasadena Seabrook La Porte Port Arthur Galveston Chattanooga Schriever Hattiesburg Sulphur Prien East Ridge Fairview Jackson Huntsville Knoxville Hernando Cleveland 18 May 19 20 21 22 23 24 25 26 27 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
Jackson Jackson, 18 May: 8.9 µg/m³ Jackson, 19 May: 11.1 µg/m³ Jackson, 20 May: 11.6 µg/m³ Jackson, 21 May: 28.9 µg/m³, 3.5× its usual 8.2 Jackson, 22 May: 29.3 µg/m³, 3.6× its usual 8.2 Jackson, 23 May: 13.0 µg/m³ Jackson, 24 May: 13.5 µg/m³ Jackson, 25 May: 20.6 µg/m³ Jackson, 26 May: 24.2 µg/m³ Jackson, 27 May: 19.8 µg/m³ Knoxville Knoxville, 18 May: 11.7 µg/m³ Knoxville, 19 May: 11.3 µg/m³ Knoxville, 20 May: 8.0 µg/m³ Knoxville, 21 May: 28.4 µg/m³, 4.2× its usual 6.7 Knoxville, 22 May: 18.7 µg/m³ Knoxville, 23 May: 18.0 µg/m³ Knoxville, 24 May: 20.3 µg/m³ Knoxville, 25 May: 20.2 µg/m³ Knoxville, 26 May: 16.7 µg/m³ Knoxville, 27 May: 6.0 µg/m³ Cleveland Cleveland, 18 May: 10.5 µg/m³ Cleveland, 19 May: 11.0 µg/m³ Cleveland, 20 May: 19.0 µg/m³ Cleveland, 21 May: 27.6 µg/m³, 4.1× its usual 6.8 Cleveland, 22 May: 32.7 µg/m³, 4.8× its usual 6.8 Cleveland, 23 May: 14.4 µg/m³ Cleveland, 24 May: 20.8 µg/m³ Cleveland, 25 May: 29.2 µg/m³ Cleveland, 26 May: 24.6 µg/m³ Cleveland, 27 May: 18.1 µg/m³ Fairview Fairview, 18 May: 9.8 µg/m³ Fairview, 19 May: 10.2 µg/m³ Fairview, 20 May: 7.9 µg/m³ Fairview, 21 May: 27.6 µg/m³, 3.6× its usual 7.7 Fairview, 22 May: 22.9 µg/m³ Fairview, 23 May: 19.2 µg/m³ Fairview, 24 May: 21.5 µg/m³ Fairview, 25 May: 23.5 µg/m³ Fairview, 26 May: 22.4 µg/m³ Fairview, 27 May: 9.9 µg/m³ East Ridge East Ridge, 18 May: 9.8 µg/m³ East Ridge, 19 May: 10.2 µg/m³ East Ridge, 20 May: 7.9 µg/m³ East Ridge, 21 May: 27.6 µg/m³, 3.6× its usual 7.7 East Ridge, 22 May: 22.9 µg/m³ East Ridge, 23 May: 19.2 µg/m³ East Ridge, 24 May: 21.5 µg/m³ East Ridge, 25 May: 23.5 µg/m³ East Ridge, 26 May: 22.4 µg/m³ East Ridge, 27 May: 9.9 µg/m³ Hernando Hernando, 18 May: 10.0 µg/m³ Hernando, 19 May: 11.4 µg/m³ Hernando, 20 May: 27.6 µg/m³ Hernando, 21 May: 27.1 µg/m³, 4.0× its usual 6.8 Hernando, 22 May: 30.9 µg/m³, 4.5× its usual 6.8 Hernando, 23 May: 17.0 µg/m³ Hernando, 24 May: 23.9 µg/m³ Hernando, 25 May: 25.9 µg/m³ Hernando, 26 May: 17.5 µg/m³ Hernando, 27 May: 15.8 µg/m³ Chattanooga Chattanooga, 18 May: 10.1 µg/m³ Chattanooga, 19 May: 9.7 µg/m³ Chattanooga, 20 May: 7.7 µg/m³ Chattanooga, 21 May: 26.7 µg/m³, 3.3× its usual 8.2 Chattanooga, 22 May: 21.2 µg/m³ Chattanooga, 23 May: 19.2 µg/m³ Chattanooga, 24 May: 21.4 µg/m³ Chattanooga, 25 May: 21.4 µg/m³ Chattanooga, 26 May: 20.3 µg/m³ Chattanooga, 27 May: 9.7 µg/m³ Huntsville Huntsville, 18 May: 7.4 µg/m³ Huntsville, 19 May: 7.4 µg/m³ Huntsville, 20 May: 8.5 µg/m³ Huntsville, 21 May: 25.4 µg/m³, 4.0× its usual 6.4 Huntsville, 22 May: 19.0 µg/m³ Huntsville, 23 May: 16.5 µg/m³ Huntsville, 24 May: 18.8 µg/m³ Huntsville, 25 May: 18.7 µg/m³ Huntsville, 26 May: 17.4 µg/m³ Huntsville, 27 May: 10.5 µg/m³ Schriever Schriever, 18 May: 10.8 µg/m³ Schriever, 19 May: 11.3 µg/m³ Schriever, 20 May: 14.7 µg/m³ Schriever, 21 May: 15.7 µg/m³ Schriever, 22 May: 28.7 µg/m³, 3.3× its usual 8.6 Schriever, 23 May: 25.0 µg/m³, 2.9× its usual 8.6 Schriever, 24 May: no reading Schriever, 25 May: no reading Schriever, 26 May: 16.5 µg/m³ Schriever, 27 May: 13.0 µg/m³ Prien Prien, 18 May: 10.0 µg/m³ Prien, 19 May: 13.0 µg/m³ Prien, 20 May: 10.9 µg/m³ Prien, 21 May: 18.0 µg/m³ Prien, 22 May: 25.7 µg/m³, 3.3× its usual 7.9 Prien, 23 May: 29.0 µg/m³, 3.5× its usual 8.2 Prien, 24 May: 24.6 µg/m³ Prien, 25 May: 17.1 µg/m³ Prien, 26 May: 25.3 µg/m³ Prien, 27 May: 23.4 µg/m³ Sulphur Sulphur, 18 May: 10.0 µg/m³ Sulphur, 19 May: 13.0 µg/m³ Sulphur, 20 May: 10.9 µg/m³ Sulphur, 21 May: 18.0 µg/m³ Sulphur, 22 May: 25.7 µg/m³, 3.3× its usual 7.9 Sulphur, 23 May: 29.0 µg/m³, 3.5× its usual 8.2 Sulphur, 24 May: 24.6 µg/m³ Sulphur, 25 May: 17.1 µg/m³ Sulphur, 26 May: 25.3 µg/m³ Sulphur, 27 May: 23.4 µg/m³ Hattiesburg Hattiesburg, 18 May: 8.7 µg/m³ Hattiesburg, 19 May: 9.2 µg/m³ Hattiesburg, 20 May: 10.2 µg/m³ Hattiesburg, 21 May: 19.2 µg/m³ Hattiesburg, 22 May: 25.6 µg/m³, 3.5× its usual 7.4 Hattiesburg, 23 May: 8.5 µg/m³ Hattiesburg, 24 May: 15.6 µg/m³ Hattiesburg, 25 May: 20.8 µg/m³ Hattiesburg, 26 May: 18.3 µg/m³ Hattiesburg, 27 May: 15.1 µg/m³ Port Arthur Port Arthur, 18 May: 11.3 µg/m³ Port Arthur, 19 May: 12.5 µg/m³ Port Arthur, 20 May: 9.8 µg/m³ Port Arthur, 21 May: 14.2 µg/m³ Port Arthur, 22 May: 25.1 µg/m³, 2.8× its usual 9.0 Port Arthur, 23 May: 24.2 µg/m³ Port Arthur, 24 May: 24.3 µg/m³ Port Arthur, 25 May: 13.8 µg/m³ Port Arthur, 26 May: 27.1 µg/m³ Port Arthur, 27 May: 22.4 µg/m³ Baytown Baytown, 18 May: 11.7 µg/m³ Baytown, 19 May: 12.3 µg/m³ Baytown, 20 May: 10.7 µg/m³ Baytown, 21 May: 17.1 µg/m³ Baytown, 22 May: 24.3 µg/m³ Baytown, 23 May: 26.3 µg/m³, 2.3× its usual 11.3 Baytown, 24 May: 27.9 µg/m³, 2.4× its usual 11.4 Baytown, 25 May: 14.2 µg/m³ Baytown, 26 May: 22.1 µg/m³ Baytown, 27 May: 21.9 µg/m³ Highlands Highlands, 18 May: 11.7 µg/m³ Highlands, 19 May: 12.3 µg/m³ Highlands, 20 May: 10.7 µg/m³ Highlands, 21 May: 17.1 µg/m³ Highlands, 22 May: 24.3 µg/m³ Highlands, 23 May: 26.3 µg/m³, 2.3× its usual 11.3 Highlands, 24 May: 27.9 µg/m³, 2.4× its usual 11.4 Highlands, 25 May: 14.2 µg/m³ Highlands, 26 May: 22.1 µg/m³ Highlands, 27 May: 21.9 µg/m³ Houston Houston, 18 May: 12.8 µg/m³ Houston, 19 May: 11.8 µg/m³ Houston, 20 May: 10.1 µg/m³ Houston, 21 May: 17.9 µg/m³ Houston, 22 May: 23.8 µg/m³ Houston, 23 May: 25.6 µg/m³, 2.1× its usual 12.0 Houston, 24 May: 24.2 µg/m³ Houston, 25 May: 13.7 µg/m³ Houston, 26 May: 21.7 µg/m³ Houston, 27 May: 22.9 µg/m³ Pasadena Pasadena, 18 May: 11.9 µg/m³ Pasadena, 19 May: 10.0 µg/m³ Pasadena, 20 May: 9.3 µg/m³ Pasadena, 21 May: 16.9 µg/m³ Pasadena, 22 May: 23.8 µg/m³ Pasadena, 23 May: 25.3 µg/m³, 2.3× its usual 10.8 Pasadena, 24 May: 27.2 µg/m³, 2.5× its usual 10.9 Pasadena, 25 May: 13.9 µg/m³ Pasadena, 26 May: 22.0 µg/m³ Pasadena, 27 May: 20.8 µg/m³ Galveston Galveston, 18 May: 9.0 µg/m³ Galveston, 19 May: 8.5 µg/m³ Galveston, 20 May: 8.6 µg/m³ Galveston, 21 May: 16.8 µg/m³ Galveston, 22 May: 22.5 µg/m³ Galveston, 23 May: 23.8 µg/m³ Galveston, 24 May: 26.6 µg/m³, 3.0× its usual 9.0 Galveston, 25 May: 12.8 µg/m³ Galveston, 26 May: 19.4 µg/m³ Galveston, 27 May: no reading Conroe Conroe, 18 May: 9.2 µg/m³ Conroe, 19 May: 13.0 µg/m³ Conroe, 20 May: 11.4 µg/m³ Conroe, 21 May: 17.7 µg/m³ Conroe, 22 May: 22.4 µg/m³ Conroe, 23 May: 23.7 µg/m³ Conroe, 24 May: 26.1 µg/m³, 2.5× its usual 10.4 Conroe, 25 May: 9.8 µg/m³ Conroe, 26 May: 20.8 µg/m³ Conroe, 27 May: 22.9 µg/m³ La Porte La Porte, 18 May: 8.7 µg/m³ La Porte, 19 May: 8.4 µg/m³ La Porte, 20 May: 8.7 µg/m³ La Porte, 21 May: 15.2 µg/m³ La Porte, 22 May: 24.2 µg/m³ La Porte, 23 May: 24.6 µg/m³ La Porte, 24 May: 25.0 µg/m³, 2.6× its usual 9.8 La Porte, 25 May: 11.8 µg/m³ La Porte, 26 May: 22.1 µg/m³ La Porte, 27 May: 19.0 µg/m³ Seabrook Seabrook, 18 May: 8.7 µg/m³ Seabrook, 19 May: 8.4 µg/m³ Seabrook, 20 May: 8.7 µg/m³ Seabrook, 21 May: 15.2 µg/m³ Seabrook, 22 May: 24.2 µg/m³ Seabrook, 23 May: 24.6 µg/m³ Seabrook, 24 May: 25.0 µg/m³, 2.6× its usual 9.8 Seabrook, 25 May: 11.8 µg/m³ Seabrook, 26 May: 22.1 µg/m³ Seabrook, 27 May: 19.0 µg/m³ 18 May 19 20 21 22 23 24 25 26 27 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. Good 0–50
Moderate 51–100
Sensitive groups 101–150
Unhealthy 151–200
Very unhealthy 201–300
Hazardous 301+
Every city it reached
City Days Highest Usual Above usual
Cleveland Mississippi, United States 2 22 May 6.8 4.8× Hernando Mississippi, United States 2 22 May 6.8 4.5× Knoxville Tennessee, United States 1 21 May 6.7 4.2× Huntsville Alabama, United States 1 21 May 6.4 4.0× Jackson Mississippi, United States 2 22 May 8.2 3.6× Fairview Georgia, United States 1 21 May 7.7 3.6× East Ridge Tennessee, United States 1 21 May 7.7 3.6× Prien Louisiana, United States 2 23 May 8.2 3.5× Sulphur Louisiana, United States 2 23 May 8.2 3.5× Hattiesburg Mississippi, United States 1 22 May 7.4 3.5× Schriever Louisiana, United States 2 22 May 8.6 3.3× Chattanooga Tennessee, United States 1 21 May 8.2 3.3× Galveston Texas, United States 1 24 May 9.0 3.0× Port Arthur Texas, United States 1 22 May 9.0 2.8× La Porte Texas, United States 1 24 May 9.8 2.6× Seabrook Texas, United States 1 24 May 9.8 2.6× Pasadena Texas, United States 2 24 May 10.9 2.5× Conroe Texas, United States 1 24 May 10.4 2.5× Baytown Texas, United States 2 24 May 11.4 2.4× Highlands Texas, United States 2 24 May 11.4 2.4× Houston Texas, United States 1 23 May 12.0 2.1×
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
Number 62 of 151 episodes in the United States since our records began, by cities reached.
Eastern United States and Canada, June and July 2023 343 Northern United States and Canada, July 2026 327 United States and Canada, July 2023 322 Eastern United States and Canada, May and June 2023 317 North-eastern United States and Canada, 29 July to 9 August 2025 292 Northern United States and Canada, May and June 2025 247 United States and Canada, June 2023 195 North-western United States and Canada, August 2023 176 North-western United States and Canada, 4 to 22 August 2026 151 Northern United States and Canada, July 2025 139 Northern United States and Canada, June 2025 134 North-western United States and Canada, July and August 2026 118 Southern United States, May 2023 21 Bars: cities reached; colour: the level of the episode's highest daily reading. All 151 .
Use this page SmogRank, Southern United States, May 2023: 21 cities with PM2.5 at twice their usual or more, 21 to 24 May 2023, smogrank.com/episodes/2023-05-southern-united-states (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.
