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Feira de Santana, Brazil's second-largest city in Bahia state, occupies a strategic position in the Agreste region—a transitional zone between the humid coastal Zona da Mata and the semi-arid Sertão interior. Situated at approximately 234 meters above sea level on the Planalto da Borborema plateau, the city's geography creates a unique air quality context. The urban area spreads across relatively flat terrain with gentle undulations, surrounded by agricultural lands producing sugarcane, cassava, and livestock. This creates an urban-rural gradient where agricultural burning occasionally contributes to particulate matter, though less intensely than in Amazonian regions. Feira de Santana lies approximately 100 kilometers northwest of Salvador, positioned along the BR-116 highway that forms Brazil's industrial backbone, attracting light manufacturing and automotive industries whose emissions mix with urban traffic pollution. The city lacks significant water bodies nearby, with only seasonal streams, reducing natural ventilation effects. Its inland location shields it from coastal breezes that might disperse pollutants, while the surrounding cerrado vegetation and agricultural zones create a landscape where dust can become airborne during dry periods. The city's rapid expansion has created urban heat island effects that can trap pollutants, particularly in the densely built central districts where narrow streets limit air circulation.

Feira de Santana experiences a tropical savanna climate with distinct wet and dry seasons that dramatically influence air quality patterns. During the dry season from September to February, pollution typically peaks as reduced rainfall allows particulate matter to accumulate. October through December sees the highest concentrations, when agricultural burning in surrounding areas combines with urban emissions under stable atmospheric conditions. These months feature temperature inversions that trap pollutants near the surface, especially during calm mornings when fog occasionally forms. Sensitive groups should limit outdoor activities during late morning hours when ozone levels build. The rainy season from March to August brings relief as frequent showers wash pollutants from the air, with June and July offering the cleanest conditions for outdoor exercise. However, high humidity during this period can sometimes react with emissions to form secondary pollutants. Wind patterns shift seasonally, with stronger easterly winds during drier months occasionally bringing dust from the interior, while weaker variable winds in transition months allow local pollution to concentrate. Asthma sufferers should be particularly cautious during the August-September transition when burning increases before rains return. The city's elevation provides some moderation of heat extremes, but thermal inversions remain a concern during cool, clear nights in the dry season.