Pihuamo, Jalisco, nestled within the fertile lowlands of western Mexico, occupies a geographically significant position within the Lake Chapala bioregion. Located at approximately 18.95° latitude and -103.167° longitude, and an elevation of roughly 1,480 meters (4,856 feet) above sea level, the town benefits from a relatively mild climate influenced by its proximity to Lake Chapala, Mexico’s largest freshwater lake. The surrounding landscape is characterized by a gradual transition from rolling hills and agricultural fields to the expansive lake basin. This area is predominantly agricultural, with maize, beans, and agave being key crops, contributing to both the local economy and potential sources of particulate matter. Pihuamo’s urban character is that of a small, rural-agricultural community, with a limited industrial presence, primarily focused on food processing and related activities. The urban–rural gradient is quite pronounced; the town itself is compact, surrounded by extensive farmland and scattered rural settlements. The lake’s presence moderates temperatures and introduces humidity, but also creates conditions conducive to fog formation, particularly during the cooler months. Topographically, the area is relatively flat, which can exacerbate the accumulation of pollutants, especially when wind patterns are weak. The regional position, within a basin, limits dispersion of airborne contaminants, making air quality particularly sensitive to local emissions and regional transport of pollutants from larger urban centers like Guadalajara, located approximately 80 kilometers to the north.

Pihuamo’s air quality experiences a distinct seasonal pattern dictated by the interplay of temperature, humidity, and prevailing wind conditions. The dry season, typically spanning from November through April, often sees a noticeable increase in particulate matter. This is due to agricultural burning practices, used for land clearing and crop residue removal, which release significant amounts of smoke and ash into the atmosphere. Temperature inversions, common during these months, trap pollutants near the ground, further worsening air quality. Fog, frequently occurring in the mornings, also contributes to the concentration of pollutants. The wet season, from May to October, brings increased rainfall and higher humidity, which naturally helps to cleanse the air by washing away particulate matter. However, periods of intense rainfall can also lead to soil erosion and dust storms, temporarily impacting air quality. During the summer months, convective thunderstorms can disrupt atmospheric stability, promoting better dispersion of pollutants. The shoulder seasons (April-May and October-November) generally offer the most favorable air quality, with moderate temperatures and increased wind speeds. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during the dry season, particularly on days with agricultural burning or dense fog. Limiting outdoor exertion and wearing masks can provide some protection. The prevalence of agricultural activity means that air quality can fluctuate significantly, even within a single day, depending on local burning practices.