Thursday, September 18, 2025

CDMX poor air quality alert remains in effect for second day

Yearning for a clear day in Mexico City? Residents had no luck with that on Wednesday as the Environmental Commission of the Megalopolis (CAMe) announced, for the second day in a row, that poor air quality conditions would continue in Mexico’s capital.

The intergovernmental coordinating agency oversees environmental protection in Mexico City and neighboring states.

People crossing a pedestrian bridge in mexico city
Heat reaching 30 C and a poor air quality rating made for an uncomfortable Wednesday for residents, who were advised to avoid public events and outdoor recreation throughout the day. (Victoria Valtierra/Cuartoscuro)

According to the Mexico City Air Quality Monitoring System (SMCA), a high-pressure weather system continued exerting influence over the Valley of Mexico on Wednesday, bringing dry and hot weather with clear skies and intense solar radiation throughout the day. 

Temperatures were expected to range between 29 C and 30 C (84 F to 86 F). Due to the lack of wind in the early afternoon, pollutants were expected to stagnate. The evening’s air quality was expected to deteriorate further, reaching “poor” to “very poor” conditions. 

To avoid health hazards, authorities urged the public to refrain from engaging in any civic, cultural or recreational activities, as well as outdoor exercise, from 1–7 p.m. Those most at risk from exposure include children, people with asthma and lung diseases, older adults and active outdoor workers.

Just after 3 p.m. today, the SMCA warned of a dangerous level of ozone detected in the Valley of Mexico municipality Cuautitlan Izcalli, located in México state.

Authorities also reminded the public that today’s Hoy No Circula restrictions apply to private vehicles with the following characteristics: 

  • A double-zero (00) or zero (0) hologram sticker and a license plate number ending in 3 or 4 equivalent to a red sticker
  • A No. 1 hologram sticker and a license plate ending in the number 1, 3, 4, 5, 7 or 9
  • Any vehicle with a No. 2 hologram sticker

Exempt vehicles include hybrid cars and those with an ecological license plate or exemption-type hologram. Vehicles that carry a valid double-zero or single-zero hologram sticker and have a yellow, pink, green or blue sticker are also exempt.

The Hoy No Circula program, which has been in place since 1989, seeks to reduce emissions in the capital by prohibiting drivers from using their vehicles in the city on a given day of the week.

Air quality in Mexico City is usually poor. The air quality index (AQI) is measured on a scale of zero to 500, with zero being perfect. On a typical day in Mexico City, AQI is around 100, mostly due to pollutants from vehicle emissions. 

Over 5 million cars drive through Mexico City every day, releasing carbon monoxide, hydrocarbons and nitrogen oxides into the air. Because the city sits in a high-elevation basin, contaminants rise and hover over the metropolitan area.

The CAMe will issue updated air quality bulletins throughout the day on the social media platform X.

Mexico News Daily

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