Autlán de Navarro, nestled in the state of Jalisco, Mexico, occupies a strategically important position within the broader Lake Chapala bioregion. Located at approximately 19.7667° N, 104.3667° W and an elevation of around 1,100 meters (3,600 feet) above sea level, the city sits within a valley carved by the Autlán River, a tributary of the Ameca River. This valley setting, while providing some shelter from prevailing winds, also contributes to localized air quality challenges. The surrounding landscape is a mosaic of rolling hills and agricultural land, primarily dedicated to sugarcane and coffee cultivation, interspersed with patches of tropical dry forest. To the west lies the expansive Lake Chapala, Mexico’s largest freshwater lake, which influences regional humidity and temperature patterns. The urban fabric of Autlán is characterized by a compact core, reflecting its historical role as a regional trading hub, gradually expanding outwards along the river valley. Significant industrial activity, including food processing (particularly sugar refining) and textile manufacturing, is concentrated in and around the city, contributing to localized pollution sources. The urban-rural gradient is relatively sharp, with agricultural fields and smaller rural communities transitioning quickly into the urban area. The terrain, a mix of relatively flat valley floor and steeper slopes, impacts ventilation patterns; stagnant air can accumulate in lower-lying areas, particularly during periods of calm weather. The proximity to both agricultural zones and industrial activity creates a complex interplay of potential pollutants, impacting air quality dynamics.

Autlán de Navarro experiences a tropical savanna climate, characterized by distinct wet and dry seasons, significantly influencing its air quality profile. The dry season, typically spanning from November to April, often sees a noticeable increase in particulate matter. Reduced rainfall and lower humidity contribute to the accumulation of dust and emissions from agricultural burning, a common practice for land preparation. Temperature inversions, where a layer of warm air traps cooler air near the ground, are more frequent during these months, exacerbating the problem by preventing pollutants from dispersing. Conversely, the wet season (May to October) brings increased rainfall and higher humidity, naturally cleansing the atmosphere and reducing particulate concentrations. However, periods of intense rainfall can also lead to flooding, potentially releasing pollutants from contaminated sites. The monsoon-like rains during the wet season generally improve air quality, though localized flooding can temporarily worsen conditions. Fog, particularly in the early morning during the dry season, can trap pollutants close to the ground, creating localized pockets of poor air quality. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during the dry season, particularly during agricultural burning periods (typically January-March). Outdoor activities are generally more favorable during the wet season, although vigilance regarding flood-related hazards is essential. The transition months (April and October) often present variable air quality, influenced by shifting weather patterns and the interplay between dry and wet season conditions.