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Matehuala, nestled in the rugged altiplano of San Luis Potosí, Mexico, occupies a geographically significant position within the Huasteca Potosina region. Located at approximately 23.65°N, 100.64°W and an elevation of around 1,438 meters (4,718 feet) above sea level, the city’s topography is dominated by rolling hills and valleys, characteristic of the Sierra Madre Oriental foothills. This terrain influences local wind patterns, often creating stagnant air conditions, particularly during periods of atmospheric stability. The surrounding landscape is a mosaic of arid scrubland, transitioning into pine-oak forests at higher elevations, and extensive agricultural fields dedicated to maize, beans, and livestock grazing. Matehuala serves as a crucial transportation hub, lying along the Mexican Federal Highway 40, connecting it to major industrial centers like Monterrey and San Luis Potosí City. This connectivity, while economically vital, contributes to vehicular emissions. The city’s urban character is a blend of traditional colonial architecture and modern development, with a gradual urban–rural gradient extending outwards into the agricultural plains. The relative scarcity of large bodies of water in the immediate vicinity—the nearby Río Españita being a minor tributary—limits natural air purification processes. While not directly adjacent to a major industrial belt, the agricultural activity and transportation corridors contribute to localized pollution sources, and the city’s location within a broad, semi-arid zone can exacerbate dust and particulate matter issues, especially during dry periods. The prevailing winds, often light and variable, struggle to effectively disperse pollutants, leading to potential air quality challenges.

Matehuala experiences a distinct wet and dry season pattern, significantly impacting its air quality. The dry season, typically spanning from November through April, is characterized by lower humidity, increased solar radiation, and a higher frequency of temperature inversions. These inversions trap pollutants near the ground, leading to periods of elevated particulate matter concentrations, particularly from agricultural burning practices and vehicle exhaust. Dust storms, common during this period, further degrade air quality. The months of January and February often see the most persistent and concerning air quality conditions. Conversely, the wet season, from May to October, brings increased rainfall and higher humidity, which naturally helps to cleanse the atmosphere by washing away pollutants and suppressing dust. However, periods of intense rainfall can also lead to localized flooding and the release of pollutants from inundated areas. The increased cloud cover during the wet season reduces solar radiation, which can impact the formation of ozone, a secondary pollutant. Wind patterns are generally more variable during the wet season, offering better dispersion of pollutants. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during the dry season, limiting outdoor activities during peak pollution episodes. Agricultural workers should be particularly mindful of smoke exposure during controlled burns. Maintaining vehicle maintenance and reducing unnecessary travel can contribute to improved air quality throughout the year, but are especially important during the dry season’s more challenging conditions.