Shagamu, situated in southwestern Nigeria's Ogun State, occupies a strategic position within the Lagos-Ibadan industrial corridor, approximately 60 kilometers northeast of Lagos, Africa's largest megacity. The city lies at coordinates 6.8333°N, 3.6500°E, with an elevation averaging around 50 meters above sea level, placing it within the coastal plain of the Gulf of Guinea. Its terrain is predominantly flat to gently undulating, characteristic of the Yoruba Plateau's southern fringes, with lateritic soils supporting both urban development and surrounding agricultural zones. Shagamu's location directly influences air quality through multiple pathways: as a transitional urban center between Lagos's intense industrial pollution and more rural inland areas, it experiences pollutant transport via prevailing southwesterly winds. The city sits near the Ogun River basin, whose seasonal flooding can create stagnant air pockets, while proximity to the Atlantic Ocean (about 40 kilometers south) brings maritime influences that occasionally disperse pollutants. Surrounding landscapes include mixed farmland—notably cocoa, kolanut, and cassava plantations—whose burning during land preparation contributes seasonal particulate matter. The urban-rural gradient shows denser commercial and residential areas in the city core, with peri-urban zones blending into agricultural hinterlands. Shagamu's position along major transport routes (including the Lagos-Ibadan Expressway) exposes it to vehicular emissions, while local industries like food processing and textiles add point-source pollution. The city's growth as a satellite to Lagos has accelerated urbanization without proportional air quality controls, creating a complex pollution profile shaped by geography, regional industry, and climate interactions.

Shagamu's air quality follows distinct seasonal patterns driven by West Africa's monsoon climate, though specific AQI data is limited. During the dry season (November to March), harmattan winds from the Sahara Desert transport fine dust particles southward, typically peaking from December to February. These months see elevated particulate matter (PM2.5 and PM10) levels, reducing visibility and exacerbating respiratory conditions—sensitive groups like asthmatics should limit outdoor activities, especially in early mornings when inversions trap pollutants. The transition to the rainy season (April to October) brings relief: April's first rains wash away accumulated dust, while the peak monsoon (June to September) with frequent thunderstorms and southwesterly winds from the Atlantic disperses pollutants effectively. However, July and August can experience brief pollution spikes after heavy rains due to increased humidity and mold spores. The minor dry period in August (known as 'August break') may see temporary pollutant accumulation. For outdoor enthusiasts, the best months are typically May-June and September-October, when rainfall cleanses the air without excessive humidity. Sensitive populations should monitor symptoms during harmattan months and use air purifiers indoors; all residents should avoid burning waste during dry periods. Weather hazards like fog are rare, but temperature inversions occasionally occur in dry-season nights, trapping vehicle emissions near the ground. Understanding these seasonal rhythms allows residents to plan activities and protect health amid Shagamu's evolving urban atmosphere.