Saltillo, the capital of Coahuila state in northeastern Mexico, occupies a strategic position in the arid highlands of the Sierra Madre Oriental mountain range at approximately 1,600 meters (5,250 feet) above sea level. This elevated basin location creates a distinctive urban geography where the city is surrounded by rugged, semi-desert terrain with sparse vegetation, contributing to natural dust generation that can exacerbate particulate pollution. Saltillo lies within Mexico's industrial heartland known as the 'Norte' region, positioned roughly 90 kilometers southwest of Monterrey, forming part of an interconnected urban-industrial corridor that includes automotive manufacturing, metalworking, and cement production facilities. The city's urban-rural gradient shows dense central development gradually giving way to industrial parks on the periphery, particularly to the north and east, where factories interface with agricultural zones growing crops like maize and beans in the limited arable valleys. No major rivers or large bodies of water moderate the local climate, though seasonal arroyos (dry creek beds) can channel dust during dry periods. This geography creates a semi-enclosed airshed where pollutants from urban traffic, industrial emissions, and natural dust can accumulate, especially during temperature inversions common in the high-altitude basin. The surrounding mountains partially block prevailing winds from the Gulf of Mexico, reducing natural ventilation while occasionally funneling dust storms from the Chihuahuan Desert to the northwest.

Saltillo's air quality follows distinct seasonal patterns shaped by its high-altitude desert climate. During winter (December-February), cold, stable conditions frequently create temperature inversions that trap pollutants near the surface, particularly overnight and early morning when industrial and vehicular emissions combine with residential heating sources. This season sees the highest pollution concentrations, with January typically being the worst month for sensitive groups to limit prolonged outdoor exertion. Spring (March-May) brings increasing temperatures and occasional dust storms as dry winds sweep across the surrounding semi-desert landscape, elevating particulate levels despite better atmospheric mixing. Summer (June-August) offers the cleanest air as monsoon moisture from the Gulf of Mexico arrives in July-August, with afternoon thunderstorms and increased winds effectively dispersing pollutants, though ozone can temporarily rise on hot, sunny days before rains arrive. Autumn (September-November) transitions back to drier conditions with generally good air quality in September-October before inversion season begins in November. Sensitive individuals including those with respiratory conditions should monitor air quality alerts most carefully during winter inversion episodes and spring dust events, scheduling outdoor activities for afternoon hours when mixing is better. The city's elevation means UV radiation remains strong year-round, compounding respiratory irritation during high pollution periods.