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Piraçununga, nestled in the heart of São Paulo state, Brazil, occupies a strategic position within the Paraíba River basin, approximately 280 kilometers northwest of the state capital. Its coordinates, -21.9961, -47.4258, place it on relatively flat terrain, characteristic of the São Paulo Plateau, with an average elevation of around 480 meters above sea level. The city’s geography is defined by the meandering Paraíba do Sul River, which provides a vital water source and influences local microclimates. Surrounding Piraçununga is a predominantly agricultural landscape, dominated by sugarcane plantations and cattle ranches, a typical feature of the interior São Paulo region. This agricultural activity contributes to the regional economy but also presents potential air quality challenges related to biomass burning during harvest seasons. The urban–rural gradient transitions smoothly, with smaller settlements and agricultural fields gradually giving way to the city’s built environment. While not directly adjacent to major industrial belts, Piraçununga benefits from its proximity to larger urban centers like São José do Rio Preto and Bauru, which can influence regional air pollution patterns through transport of pollutants. The relatively open terrain and prevailing winds generally facilitate dispersion of pollutants, but stagnant air conditions, particularly during certain times of the year, can lead to localized air quality degradation. The river's presence moderates temperatures and contributes to humidity, impacting the behavior of airborne particles.

Piraçununga experiences a tropical savanna climate, characterized by a distinct wet and dry season rather than four traditional seasons. The dry season, typically spanning from April to September, often sees a noticeable increase in air quality concerns. During this period, reduced rainfall and lower humidity create conditions conducive to the accumulation of particulate matter. Agricultural practices, particularly sugarcane burning for land clearing and harvesting, become more prevalent, releasing significant amounts of smoke and ash into the atmosphere. Temperature inversions, where cooler air is trapped beneath a layer of warmer air, are also more frequent during the dry season, hindering vertical mixing and further concentrating pollutants near the ground. The wet season, from October to March, brings increased rainfall and higher humidity, which naturally helps to cleanse the air by washing away particulate matter and diluting gaseous pollutants. However, intense rainfall events can occasionally lead to flooding and the release of pollutants from inundated areas. Months like August and September, coinciding with peak sugarcane harvesting, are generally periods to exercise caution, particularly for individuals with respiratory sensitivities. During the wet season, outdoor activities are generally more favorable, but vigilance regarding potential flooding-related air quality issues is still advised. Sensitive groups, including children, the elderly, and those with pre-existing respiratory conditions, should monitor local air quality reports and limit outdoor exposure during periods of elevated particulate matter, especially during the dry season’s agricultural burning activities.