SmogRank / Episodes / Mexico

Northern Mexico and United States, January 2023

For 2 days, from 28 to 29 January 2023, 8 cities in Mexico and the United States had PM2.5 at least twice their usual for the time of year. The worst reading was Ciudad Benito Juárez, Nuevo León, Mexico: 96.0 µg/m³ on 28 January, about 3.5× its usual 27.4. Ended 29 January.

No cause namedWe have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached8in 2 countries
Days228 to 29 January 2023
Worst day28 January6 cities counted
Furthest above usual5.6×García

Day by day

28 January 6 cities at twice their usual or more
EdinburgHeroica MatamorosLaredoCorpus ChristiCadereyta JiménezCiudad ApodacaPort IsabelCiudad General EscobedoSanta CatarinaCiudad Benito JuárezMonterreyGarcía
25 Jan2627282930311 Feb
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

Ciudad Benito JuárezCiudad Benito Juárez, 25 January: 12.5 µg/m³Ciudad Benito Juárez, 26 January: 18.0 µg/m³Ciudad Benito Juárez, 27 January: 30.5 µg/m³Ciudad Benito Juárez, 28 January: 96.0 µg/m³, 3.5× its usual 27.4Ciudad Benito Juárez, 29 January: 79.3 µg/m³, 3.1× its usual 25.8Ciudad Benito Juárez, 30 January: 26.1 µg/m³Ciudad Benito Juárez, 31 January: no readingCiudad Benito Juárez, 1 February: no readingMonterreyMonterrey, 25 January: 11.7 µg/m³Monterrey, 26 January: 11.0 µg/m³Monterrey, 27 January: 24.4 µg/m³Monterrey, 28 January: 82.5 µg/m³, 4.4× its usual 18.6Monterrey, 29 January: 47.5 µg/m³, 2.6× its usual 18.5Monterrey, 30 January: 20.8 µg/m³Monterrey, 31 January: no readingMonterrey, 1 February: no readingGarcíaGarcía, 25 January: 16.1 µg/m³García, 26 January: 11.4 µg/m³García, 27 January: 31.3 µg/m³García, 28 January: 71.7 µg/m³, 5.6× its usual 12.7García, 29 January: 44.0 µg/m³, 3.4× its usual 12.8García, 30 January: 19.2 µg/m³García, 31 January: no readingGarcía, 1 February: no readingSanta CatarinaSanta Catarina, 25 January: 12.1 µg/m³Santa Catarina, 26 January: 11.7 µg/m³Santa Catarina, 27 January: 30.0 µg/m³Santa Catarina, 28 January: 69.9 µg/m³, 3.1× its usual 22.7Santa Catarina, 29 January: 42.3 µg/m³Santa Catarina, 30 January: 21.0 µg/m³Santa Catarina, 31 January: no readingSanta Catarina, 1 February: no readingCiudad General Esco…Ciudad General Escobedo, 25 January: 7.6 µg/m³Ciudad General Escobedo, 26 January: 8.4 µg/m³Ciudad General Escobedo, 27 January: 22.0 µg/m³Ciudad General Escobedo, 28 January: 55.0 µg/m³, 2.7× its usual 20.2Ciudad General Escobedo, 29 January: 35.3 µg/m³Ciudad General Escobedo, 30 January: 16.3 µg/m³Ciudad General Escobedo, 31 January: no readingCiudad General Escobedo, 1 February: no readingCiudad ApodacaCiudad Apodaca, 25 January: 14.3 µg/m³Ciudad Apodaca, 26 January: 13.2 µg/m³Ciudad Apodaca, 27 January: 19.9 µg/m³Ciudad Apodaca, 28 January: 48.6 µg/m³, 2.6× its usual 18.7Ciudad Apodaca, 29 January: 50.0 µg/m³, 2.6× its usual 19.0Ciudad Apodaca, 30 January: 22.4 µg/m³Ciudad Apodaca, 31 January: no readingCiudad Apodaca, 1 February: no readingCadereyta JiménezCadereyta Jiménez, 25 January: 8.9 µg/m³Cadereyta Jiménez, 26 January: 14.3 µg/m³Cadereyta Jiménez, 27 January: 13.1 µg/m³Cadereyta Jiménez, 28 January: 33.3 µg/m³Cadereyta Jiménez, 29 January: 39.7 µg/m³, 2.1× its usual 19.1Cadereyta Jiménez, 30 January: 15.5 µg/m³Cadereyta Jiménez, 31 January: no readingCadereyta Jiménez, 1 February: no readingPort IsabelPort Isabel, 25 January: 3.5 µg/m³Port Isabel, 26 January: 5.0 µg/m³Port Isabel, 27 January: 5.7 µg/m³Port Isabel, 28 January: 21.2 µg/m³Port Isabel, 29 January: 25.4 µg/m³, 2.7× its usual 9.5Port Isabel, 30 January: 23.6 µg/m³Port Isabel, 31 January: 4.5 µg/m³Port Isabel, 1 February: no reading25 Jan2627282930311 Feb
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
GarcíaNuevo León, Mexico2 71.728 January12.75.6×
MonterreyNuevo León, Mexico2 82.528 January18.64.4×
Ciudad Benito JuárezNuevo León, Mexico2 96.028 January27.43.5×
Santa CatarinaNuevo León, Mexico1 69.928 January22.73.1×
Ciudad General EscobedoNuevo León, Mexico1 55.028 January20.22.7×
Port IsabelTexas, United States1 25.429 January9.52.7×
Ciudad ApodacaNuevo León, Mexico2 50.029 January19.02.6×
Cadereyta JiménezNuevo León, Mexico1 39.729 January19.12.1×

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 Mexico and the United States

Number 163 of 163 episodes in Mexico and the United States since our records began, by cities reached.

Bars: cities reached; colour: the level of the episode's highest daily reading. All 163.

Use this page

SmogRank, Northern Mexico and United States, January 2023: 8 cities with PM2.5 at twice their usual or more, 28 to 29 January 2023, smogrank.com/episodes/2023-01-northern-mexico-and-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.