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Nnewi, located in southeastern Nigeria's Anambra State, occupies a strategic position within the densely populated Igbo heartland, approximately 40 kilometers southeast of Onitsha along the banks of the Idemili River. Situated at coordinates 6.0167°N, 6.9167°E with an elevation around 100 meters above sea level, the city lies within Nigeria's tropical rainforest belt, characterized by gently undulating terrain that transitions from urban core to peri-urban agricultural zones. Nnewi's geography creates a complex air quality dynamic: its position in the Anambra Basin places it within Nigeria's industrial and commercial corridor, with proximity to major transportation routes like the Onitsha-Owerri Road facilitating both economic activity and vehicular emissions. The city's urban character as Nigeria's automotive and manufacturing hub—often called 'Japan of Africa'—means industrial emissions from numerous factories, particularly auto parts and plastics manufacturing, mix with dense residential areas lacking strict zoning. Surrounding landscapes include agricultural fields growing cassava, yams, and oil palms, whose seasonal burning contributes particulate matter, while the Idemili River provides some natural ventilation but insufficient to disperse pollutants effectively. The urban-rural gradient shows decreasing pollution toward surrounding villages, but Nnewi's compact development and limited green spaces create localized pollution hotspots where industrial, transportation, and domestic biomass burning emissions accumulate, especially during calm weather conditions.

Nnewi experiences distinct seasonal air quality patterns shaped by West Africa's tropical monsoon climate, though specific AQI data remains limited. During the dry season from November to March, pollution typically peaks due to multiple converging factors: Harmattan winds from the Sahara Desert transport fine dust particles southward, combining with local emissions from increased biomass burning for land clearing and domestic heating. December through February sees the worst conditions, with temperature inversions trapping pollutants near the ground during cool nights and mornings, creating hazy conditions that reduce visibility and increase respiratory risks. Sensitive groups like asthmatics, children, and the elderly should minimize outdoor activity during these months, especially in early mornings when inversion layers are strongest. The rainy season from April to October brings temporary relief as frequent thunderstorms and monsoon rains wash pollutants from the atmosphere, with June through August offering the cleanest air for outdoor activities. However, brief pollution spikes can occur during transitional months like April and October when agricultural burning coincides with variable winds. Throughout the year, prevailing southwesterly winds provide some dispersion, but Nnewi's location in a relatively sheltered basin means pollutants often accumulate rather than disperse efficiently. Fog occasionally forms in December and January, combining with pollution to create unhealthy smog episodes that warrant indoor air filtration use for vulnerable populations.