SmogRank / Episodes / United States

Southern United States and Mexico, March and April 2025

For 3 days, from 30 March to 1 April 2025, 8 cities in the United States and Mexico had PM2.5 at least twice their usual for the time of year. The worst reading was Saltillo, Coahuila, Mexico: 111.0 µg/m³ on 31 March, about 6.2× its usual 18.0.

No cause namedWe have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached8in 2 countries
Days330 March to 1 April 2025
Worst day31 March5 cities counted
Furthest above usual6.2×Saltillo

Day by day

31 March 5 cities at twice their usual or more
MissionCiudad Benito JuárezCiudad General EscobedoJardines de la SillaSanta CatarinaGarcíaSan AntonioGalvestonMonterreyCadereyta JiménezEdinburgBrownsvilleLaredoCorpus ChristiEagle PassSaltillo
27 Mar282930311 Apr234
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

Corpus ChristiCorpus Christi, 27 March: 12.8 µg/m³, 1.5× usualCorpus Christi, 28 March: 9.3 µg/m³, 1.1× usualCorpus Christi, 29 March: 23.0 µg/m³, 2.6× usualCorpus Christi, 30 March: 31.1 µg/m³, 3.5× usualCorpus Christi, 31 March: 31.1 µg/m³, 3.5× usualCorpus Christi, 1 April: 23.5 µg/m³, 2.7× usualCorpus Christi, 2 April: 27.5 µg/m³, 3.1× usualCorpus Christi, 3 April: 29.4 µg/m³, 3.3× usualCorpus Christi, 4 April: 27.2 µg/m³, 3.1× usualEdinburgEdinburg, 27 March: 4.7 µg/m³, 0.5× usualEdinburg, 28 March: 5.6 µg/m³, 0.6× usualEdinburg, 29 March: 20.3 µg/m³, 2.1× usualEdinburg, 30 March: 27.9 µg/m³, 2.9× usualEdinburg, 31 March: 30.6 µg/m³, 3.2× usualEdinburg, 1 April: 24.7 µg/m³, 2.6× usualEdinburg, 2 April: 23.0 µg/m³, 2.4× usualEdinburg, 3 April: 21.4 µg/m³, 2.2× usualEdinburg, 4 April: 21.8 µg/m³, 2.3× usualBrownsvilleBrownsville, 27 March: 7.4 µg/m³, 0.8× usualBrownsville, 28 March: 7.7 µg/m³, 0.9× usualBrownsville, 29 March: 22.4 µg/m³, 2.5× usualBrownsville, 30 March: 27.7 µg/m³, 3.1× usualBrownsville, 31 March: 28.5 µg/m³, 3.2× usualBrownsville, 1 April: 16.3 µg/m³, 1.8× usualBrownsville, 2 April: 20.8 µg/m³, 2.3× usualBrownsville, 3 April: 18.8 µg/m³, 2.1× usualBrownsville, 4 April: 17.6 µg/m³, 2.0× usualLaredoLaredo, 27 March: 3.2 µg/m³, 0.3× usualLaredo, 28 March: 5.5 µg/m³, 0.6× usualLaredo, 29 March: 10.3 µg/m³, 1.1× usualLaredo, 30 March: 25.9 µg/m³, 2.8× usualLaredo, 31 March: 28.2 µg/m³, 3.0× usualLaredo, 1 April: 31.3 µg/m³, 3.3× usualLaredo, 2 April: 20.0 µg/m³, 2.1× usualLaredo, 3 April: 19.1 µg/m³, 2.0× usualLaredo, 4 April: 19.7 µg/m³, 2.1× usualSaltilloSaltillo, 27 March: 31.1 µg/m³, 1.7× usualSaltillo, 28 March: 15.2 µg/m³, 0.8× usualSaltillo, 29 March: 13.8 µg/m³, 0.8× usualSaltillo, 30 March: no readingSaltillo, 31 March: 111.0 µg/m³, 6.2× usualSaltillo, 1 April: no readingSaltillo, 2 April: 10.0 µg/m³, 0.6× usualSaltillo, 3 April: 5.1 µg/m³, 0.3× usualSaltillo, 4 April: 8.5 µg/m³, 0.5× usualMonterreyMonterrey, 27 March: no readingMonterrey, 28 March: no readingMonterrey, 29 March: no readingMonterrey, 30 March: no readingMonterrey, 31 March: 28.0 µg/m³, 1.6× usualMonterrey, 1 April: 38.6 µg/m³, 2.2× usualMonterrey, 2 April: 30.5 µg/m³, 1.8× usualMonterrey, 3 April: 23.0 µg/m³, 1.3× usualMonterrey, 4 April: 25.6 µg/m³, 1.5× usualCadereyta JiménezCadereyta Jiménez, 27 March: no readingCadereyta Jiménez, 28 March: no readingCadereyta Jiménez, 29 March: no readingCadereyta Jiménez, 30 March: no readingCadereyta Jiménez, 31 March: 28.8 µg/m³, 1.9× usualCadereyta Jiménez, 1 April: 34.4 µg/m³, 2.3× usualCadereyta Jiménez, 2 April: 36.3 µg/m³, 2.5× usualCadereyta Jiménez, 3 April: 26.6 µg/m³, 1.8× usualCadereyta Jiménez, 4 April: 21.5 µg/m³, 1.5× usualEagle PassEagle Pass, 27 March: 2.0 µg/m³, 0.3× usualEagle Pass, 28 March: 3.3 µg/m³, 0.4× usualEagle Pass, 29 March: 7.9 µg/m³, 1.0× usualEagle Pass, 30 March: 20.7 µg/m³, 2.7× usualEagle Pass, 31 March: 19.6 µg/m³, 2.5× usualEagle Pass, 1 April: 28.9 µg/m³, 3.8× usualEagle Pass, 2 April: 25.1 µg/m³, 3.3× usualEagle Pass, 3 April: 22.7 µg/m³, 2.9× usualEagle Pass, 4 April: 9.7 µg/m³, 1.3× usual27 Mar282930311 Apr234
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
SaltilloCoahuila, Mexico1 111.031 March18.06.2×
Eagle PassTexas, United States1 28.91 April7.73.8×
Corpus ChristiTexas, United States2 31.130 March8.83.5×
LaredoTexas, United States3 31.31 April9.43.3×
BrownsvilleTexas, United States2 28.531 March8.93.2×
EdinburgTexas, United States2 30.631 March9.63.2×
Cadereyta JiménezNuevo León, Mexico1 36.32 April14.82.5×
MonterreyNuevo León, Mexico1 38.61 April17.42.2×

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 Mexico

Number 99 of 106 episodes in the United States and Mexico 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, Southern United States and Mexico, March and April 2025: 8 cities with PM2.5 at twice their usual or more, 30 March to 1 April 2025, smogrank.com/episodes/2025-03-southern-united-states-and-mexico (accessed 2 October 2026).

Download top 10 (PNG)

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.