SmogRank / Episodes / Mexico
Southern Mexico, January 2024
For 1 day, on 1 January 2024, 14 cities in Mexico had PM2.5 at least twice their usual for the time of year. The worst reading was Salamanca, Guanajuato, Mexico: 136.0 µg/m³ on 1 January, about 8.7× its usual 15.7.
Likely New Year fireworks It came on the night of 31 December, when smoke from fireworks often fills the air over many cities at once.
Cities reached 14 in 1 country
Days 1 1 January 2024
Worst day 1 January 14 cities counted
Furthest above usual 8.7× Salamanca
Day by day
Play 1 January 14 cities at twice their usual or more
San Martin Texmelucan de Labastida Cholula Tepeji del Río de Ocampo Zacatepec de Hidalgo San Salvador Tizatlalli Toluca San Francisco Tlalcilalcalpan Veracruz San Juan del Río San Luis de la Paz Morelia Guanajuato Tula de Allende Minatitlán San Andrés Tuxtla San Miguel de Allende León de los Aldama Abasolo Mixquiahuala de Juárez Tehuacán Puebla Santiago de Querétaro Silao de la Victoria Irapuato Celaya Salamanca 29 Dec 30 31 1 Jan 2 3 4 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
Salamanca Salamanca, 29 December: 15.1 µg/m³, 1.0× usual Salamanca, 30 December: 12.7 µg/m³, 0.8× usual Salamanca, 31 December: 30.7 µg/m³, 2.0× usual Salamanca, 1 January: 136.0 µg/m³, 8.7× usual Salamanca, 2 January: 18.2 µg/m³, 1.2× usual Salamanca, 3 January: 19.5 µg/m³, 1.2× usual Salamanca, 4 January: 13.6 µg/m³, 0.9× usual Santiago de Queréta… Santiago de Querétaro, 29 December: 10.3 µg/m³, 0.7× usual Santiago de Querétaro, 30 December: 10.3 µg/m³, 0.7× usual Santiago de Querétaro, 31 December: 28.8 µg/m³, 2.0× usual Santiago de Querétaro, 1 January: 61.9 µg/m³, 4.2× usual Santiago de Querétaro, 2 January: 15.0 µg/m³, 1.0× usual Santiago de Querétaro, 3 January: 17.2 µg/m³, 1.2× usual Santiago de Querétaro, 4 January: 13.3 µg/m³, 0.9× usual Irapuato Irapuato, 29 December: 15.4 µg/m³, 0.8× usual Irapuato, 30 December: 16.4 µg/m³, 0.8× usual Irapuato, 31 December: 31.0 µg/m³, 1.5× usual Irapuato, 1 January: 104.0 µg/m³, 5.1× usual Irapuato, 2 January: 19.3 µg/m³, 1.0× usual Irapuato, 3 January: 19.0 µg/m³, 0.9× usual Irapuato, 4 January: 11.6 µg/m³, 0.6× usual Silao de la Victoria Silao de la Victoria, 29 December: 20.7 µg/m³, 1.0× usual Silao de la Victoria, 30 December: 18.5 µg/m³, 0.9× usual Silao de la Victoria, 31 December: 28.3 µg/m³, 1.4× usual Silao de la Victoria, 1 January: 98.6 µg/m³, 4.7× usual Silao de la Victoria, 2 January: 23.2 µg/m³, 1.1× usual Silao de la Victoria, 3 January: 19.5 µg/m³, 0.9× usual Silao de la Victoria, 4 January: 14.7 µg/m³, 0.7× usual Celaya Celaya, 29 December: 23.2 µg/m³, 1.2× usual Celaya, 30 December: 22.7 µg/m³, 1.2× usual Celaya, 31 December: 30.4 µg/m³, 1.6× usual Celaya, 1 January: 97.6 µg/m³, 5.2× usual Celaya, 2 January: 24.0 µg/m³, 1.3× usual Celaya, 3 January: 25.7 µg/m³, 1.4× usual Celaya, 4 January: 23.5 µg/m³, 1.2× usual Puebla Puebla, 29 December: 18.3 µg/m³, 0.9× usual Puebla, 30 December: 7.4 µg/m³, 0.3× usual Puebla, 31 December: 13.9 µg/m³, 0.7× usual Puebla, 1 January: 86.0 µg/m³, 4.1× usual Puebla, 2 January: 24.9 µg/m³, 1.2× usual Puebla, 3 January: 27.4 µg/m³, 1.3× usual Puebla, 4 January: 20.9 µg/m³, 1.0× usual Mixquiahuala de Juá… Mixquiahuala de Juárez, 29 December: 16.1 µg/m³, 0.8× usual Mixquiahuala de Juárez, 30 December: 15.4 µg/m³, 0.8× usual Mixquiahuala de Juárez, 31 December: 28.0 µg/m³, 1.4× usual Mixquiahuala de Juárez, 1 January: 64.2 µg/m³, 3.2× usual Mixquiahuala de Juárez, 2 January: 30.4 µg/m³, 1.5× usual Mixquiahuala de Juárez, 3 January: 21.7 µg/m³, 1.1× usual Mixquiahuala de Juárez, 4 January: 19.6 µg/m³, 1.0× usual León de los Aldama León de los Aldama, 29 December: 14.0 µg/m³, 0.8× usual León de los Aldama, 30 December: 13.4 µg/m³, 0.7× usual León de los Aldama, 31 December: 17.3 µg/m³, 1.0× usual León de los Aldama, 1 January: 51.9 µg/m³, 2.9× usual León de los Aldama, 2 January: 18.4 µg/m³, 1.0× usual León de los Aldama, 3 January: 15.4 µg/m³, 0.9× usual León de los Aldama, 4 January: 12.0 µg/m³, 0.7× usual Tehuacán Tehuacán, 29 December: 8.1 µg/m³, 0.5× usual Tehuacán, 30 December: 4.1 µg/m³, 0.3× usual Tehuacán, 31 December: 19.2 µg/m³, 1.2× usual Tehuacán, 1 January: 50.3 µg/m³, 3.2× usual Tehuacán, 2 January: 17.2 µg/m³, 1.1× usual Tehuacán, 3 January: 18.5 µg/m³, 1.2× usual Tehuacán, 4 January: 19.1 µg/m³, 1.2× usual Abasolo Abasolo, 29 December: 10.7 µg/m³, 0.7× usual Abasolo, 30 December: 10.5 µg/m³, 0.7× usual Abasolo, 31 December: 28.1 µg/m³, 1.8× usual Abasolo, 1 January: 48.9 µg/m³, 3.2× usual Abasolo, 2 January: 12.4 µg/m³, 0.8× usual Abasolo, 3 January: 13.3 µg/m³, 0.9× usual Abasolo, 4 January: 8.1 µg/m³, 0.5× usual San Andrés Tuxtla San Andrés Tuxtla, 29 December: 10.0 µg/m³, 0.7× usual San Andrés Tuxtla, 30 December: 4.6 µg/m³, 0.3× usual San Andrés Tuxtla, 31 December: 19.5 µg/m³, 1.3× usual San Andrés Tuxtla, 1 January: 40.3 µg/m³, 2.7× usual San Andrés Tuxtla, 2 January: 22.3 µg/m³, 1.5× usual San Andrés Tuxtla, 3 January: 23.5 µg/m³, 1.6× usual San Andrés Tuxtla, 4 January: 18.6 µg/m³, 1.2× usual Tula de Allende Tula de Allende, 29 December: 14.1 µg/m³, 0.8× usual Tula de Allende, 30 December: 15.6 µg/m³, 0.9× usual Tula de Allende, 31 December: 21.2 µg/m³, 1.2× usual Tula de Allende, 1 January: 35.1 µg/m³, 2.0× usual Tula de Allende, 2 January: 18.5 µg/m³, 1.1× usual Tula de Allende, 3 January: 14.9 µg/m³, 0.9× usual Tula de Allende, 4 January: 9.7 µg/m³, 0.6× usual San Miguel de Allen… San Miguel de Allende, 29 December: 13.0 µg/m³, 1.0× usual San Miguel de Allende, 30 December: 9.8 µg/m³, 0.8× usual San Miguel de Allende, 31 December: 20.0 µg/m³, 1.6× usual San Miguel de Allende, 1 January: 34.7 µg/m³, 2.8× usual San Miguel de Allende, 2 January: 15.5 µg/m³, 1.3× usual San Miguel de Allende, 3 January: 11.1 µg/m³, 0.9× usual San Miguel de Allende, 4 January: 8.8 µg/m³, 0.7× usual Minatitlán Minatitlán, 29 December: 7.9 µg/m³, 0.7× usual Minatitlán, 30 December: 4.6 µg/m³, 0.4× usual Minatitlán, 31 December: 17.8 µg/m³, 1.5× usual Minatitlán, 1 January: 31.2 µg/m³, 2.7× usual Minatitlán, 2 January: 18.1 µg/m³, 1.6× usual Minatitlán, 3 January: 21.4 µg/m³, 1.8× usual Minatitlán, 4 January: no reading 29 Dec 30 31 1 Jan 2 3 4 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
Salamanca Guanajuato, Mexico 1 1 January 15.7 8.7× Celaya Guanajuato, Mexico 1 1 January 18.9 5.2× Irapuato Guanajuato, Mexico 1 1 January 20.3 5.1× Silao de la Victoria Guanajuato, Mexico 1 1 January 20.9 4.7× Santiago de Querétaro Querétaro, Mexico 1 1 January 14.7 4.2× Puebla Puebla, Mexico 1 1 January 21.2 4.1× Tehuacán Puebla, Mexico 1 1 January 15.5 3.2× Mixquiahuala de Juárez Hidalgo, Mexico 1 1 January 19.8 3.2× Abasolo Guanajuato, Mexico 1 1 January 15.5 3.2× León de los Aldama Guanajuato, Mexico 1 1 January 18.1 2.9× San Miguel de Allende Guanajuato, Mexico 1 1 January 12.4 2.8× Minatitlán Veracruz, Mexico 1 1 January 11.6 2.7× San Andrés Tuxtla Veracruz, Mexico 1 1 January 15.0 2.7× Tula de Allende Hidalgo, Mexico 1 1 January 17.2 2.0×
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 Mexico
Number 4 of 16 episodes in Mexico since our records began, by cities reached.
Southern Mexico, January 2026 20 Southern United States and Mexico, June 2023 17 Southern Mexico, June 2024 16 Southern Mexico, January 2024 14 Southern Mexico, January 2026 12 Northern Mexico and United States, May 2025 12 Southern Mexico, December 2023 10 Guanajuato and Jalisco, Mexico, June 2023 10 Hidalgo and Puebla, Mexico, November 2025 9 Guanajuato, Mexico, December 2024 9 Southern United States and Mexico, April 2024 9 Southern United States and Mexico, March and April 2025 8 Bars: cities reached; colour: the level of the episode's highest daily reading. All 16 .
Use this page SmogRank, Southern Mexico, January 2024: 14 cities with PM2.5 at twice their usual or more, 1 January 2024, smogrank.com/episodes/2024-01-southern-mexico (accessed 3 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.
