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Tepatitlán de Morelos sits prominently within the Los Altos region of Jalisco, acting as a vital economic engine for the Mexican highlands. Perched at an elevation of approximately 1,800 metres, the city is characterized by its undulating plateau terrain and a semi-arid climate that shapes its urban morphology. The urban character is a blend of colonial heritage and rapid commercial expansion, serving as a nexus for the surrounding agricultural hinterland. Geographically, the city is cradled by rolling hills that create a natural basin effect, which significantly influences the dispersion of atmospheric pollutants. Unlike coastal cities, Tepatitlán lacks the moderating influence of large bodies of water, leading to more extreme diurnal temperature swings. The surrounding landscape is dominated by intensive livestock farming, particularly poultry and swine production, which creates a distinct urban-rural gradient where agricultural emissions merge with urban smog. This proximity to industrial-scale farming introduces ammonia and organic particulates into the air, while the surrounding dust-prone plains contribute to elevated PM10 levels. The regional position as a logistics hub for agricultural exports increases heavy-duty vehicle traffic, adding nitrogen oxides to the local atmospheric cocktail. Consequently, the interplay between the basin-like topography and the intense agricultural activity creates a unique air quality profile where pollutants often linger near the surface, particularly during stagnant atmospheric conditions, making the geographic placement of Tepatitlán a primary driver of its environmental challenges and complex public health considerations throughout the entire calendar year.

The air quality narrative in Tepatitlán de Morelos is dictated by the binary shift between the dry and rainy seasons. From November through May, the city experiences a pronounced dry period where atmospheric stability leads to frequent temperature inversions. During these winter months, cold air traps pollutants—including vehicle exhaust and agricultural particulates—close to the ground, causing AQI levels to climb. Spring is often the most challenging period, as the combination of residual dryness and agricultural biomass burning for field preparation sends smoke and fine particulate matter drifting through the urban core. Consequently, sensitive groups, such as asthmatics and the elderly, should limit outdoor exertion during the early morning hours of March and April. As the monsoon-like rains arrive in June, the atmospheric dynamic shifts dramatically. Heavy precipitation provides a natural scrubbing mechanism, washing particulate matter from the sky and significantly lowering pollution concentrations. The summer and early autumn months generally offer the cleanest air, making them ideal for outdoor activities and tourism. However, high humidity can sometimes exacerbate the feeling of air heaviness. Towards October, as the rains subside, a transitional phase begins where dust once again becomes a factor. For residents, the primary health guidance is to monitor wind patterns during the dry season and utilize air filtration during the spring burning peak to mitigate respiratory irritation caused by the intersection of livestock emissions and seasonal smoke plumes.