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Tehuacán occupies a distinctive position in southeastern Puebla, Mexico, nestled within the Tehuacán Valley—a semi-arid basin that forms part of the broader Mixteca Alta region. Situated at approximately 1,600 meters above sea level, the city's elevation contributes to a moderate climate but also creates a topographic bowl effect that can trap pollutants. This valley is flanked by the Sierra Madre Oriental to the east and the Sierra Mixteca to the west, creating a natural enclosure that limits atmospheric dispersion. The urban area itself blends into surrounding agricultural zones, particularly known for irrigated crops and greenhouse farming, which introduce particulate matter and agricultural emissions into the airshed. Proximity to the dry bed of the Río Salado and seasonal streams means dust can be a concern during arid periods. Tehuacán's growth as an industrial hub, especially in textiles and beverages, adds point-source pollution within the urban–rural gradient, where manufacturing facilities often border residential areas. The city's location away from major coastlines means it lacks the cleansing sea breezes found in coastal Mexican cities, while its position in a valley exacerbates temperature inversions, particularly in cooler months, leading to stagnant air conditions that concentrate vehicular and industrial emissions. This geographic setting makes Tehuacán's air quality highly sensitive to local meteorology and urban activities, with pollutants accumulating more readily than in more open or elevated terrains.

In Tehuacán, air quality follows a distinct seasonal rhythm shaped by the valley's semi-arid climate and meteorological patterns. During winter (December–February), cooler temperatures often lead to temperature inversions, where a layer of warm air traps pollutants near the surface, resulting in higher pollution levels, especially in mornings; sensitive groups like those with respiratory conditions should limit outdoor activities during these periods. Spring (March–May) brings warmer conditions and occasional winds that help disperse pollutants, making it a favourable time for outdoor pursuits, though dust from agricultural activities and dry landscapes can spike particulate matter. Summer (June–August) sees the rainy season, with monsoon-like showers that wash pollutants from the air, leading to cleaner conditions; however, high humidity can sometimes combine with emissions to form ground-level ozone on hot, sunny days. Autumn (September–November) transitions to drier weather, with reduced rainfall allowing pollutants to accumulate again, particularly from increased agricultural burning and urban emissions; this period may see a gradual rise in pollution levels. Throughout the year, wind patterns are generally light, limiting natural ventilation, and fog is rare but can occur in cooler months, potentially worsening visibility and pollution retention. For health guidance, sensitive individuals should monitor local air quality reports, avoid strenuous activities during inversion episodes, and consider indoor air filtration during peak pollution months, which typically align with the dry seasons.