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Bom Jesus, Piauí, nestled in Brazil’s Northeast region, occupies a geographically significant position within the vast Sertão landscape. Located at approximately -9.0739° latitude and -44.3589° longitude, the city’s terrain is characterized by undulating plains and gently sloping hills, typical of the Brazilian Highlands. The surrounding landscape is predominantly semi-arid, a mosaic of scrubland (caatinga biome) interspersed with pockets of agricultural activity, primarily subsistence farming and livestock grazing. Elevation ranges from roughly 400 to 600 meters above sea level, influencing local weather patterns and air circulation. Bom Jesus sits relatively far from major river systems; the nearest significant water body is the Rio Parnaíba, a considerable distance away, limiting the moderating influence of large bodies of water on local humidity and temperature. The urban–rural gradient transitions rapidly, with the city bordered by extensive agricultural lands and sparsely populated rural settlements. While Bom Jesus itself is a small municipality, its regional importance stems from its role as a service center for surrounding agricultural communities. There are no major industrial belts directly adjacent to Bom Jesus, however, agricultural practices, including burning for land clearing (though increasingly regulated), and the use of machinery contribute to localized air quality concerns. The prevailing winds, generally from the east, can transport pollutants from nearby agricultural areas, impacting air quality within the city limits. The caatinga vegetation, while resilient, can also contribute to particulate matter during the dry season when leaf litter accumulates.

Bom Jesus experiences a distinctly tropical climate with a pronounced wet and dry season, significantly impacting air quality throughout the year. The dry season, typically spanning from April to September, is characterized by intense heat, low humidity, and infrequent rainfall. This period often sees a build-up of particulate matter due to reduced precipitation to wash pollutants from the atmosphere and increased dust from agricultural activities and unpaved roads. Temperature inversions, common during the cooler nights of the dry season, trap pollutants near the ground, exacerbating air quality issues. The months of July and August are generally the most challenging for air quality, with increased respiratory sensitivities reported. Conversely, the wet season (October to March) brings relief as frequent rainfall effectively clears the atmosphere. Increased humidity also helps to suppress dust generation. However, periods of intense rainfall can lead to flooding and the release of mold spores, potentially affecting indoor air quality. Wind patterns shift during the wet season, often bringing moisture-laden air from the east, which can temporarily dilute pollutants. Sensitive groups, including children, the elderly, and individuals with pre-existing respiratory conditions, should exercise caution during the dry season, limiting strenuous outdoor activities during peak heat and avoiding areas with visible dust. During the wet season, vigilance regarding indoor mold is advised, ensuring adequate ventilation and addressing any water damage promptly. The transition periods between seasons can be unpredictable, with fluctuating air quality depending on rainfall patterns and wind conditions.