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Villupuram occupies a strategic position in northern Tamil Nadu, situated approximately 160 kilometers southwest of Chennai and 40 kilometers inland from the Bay of Bengal. This district headquarters city lies at a modest elevation of around 45 meters above sea level within the flat, alluvial plains of the Pennar River basin, characterized by gently undulating terrain that transitions into the Eastern Ghats foothills to the west. The city's urban character blends administrative functions with agricultural market services, creating a distinct urban-rural gradient where built-up areas merge with extensive paddy fields, sugarcane plantations, and coconut groves. Villupuram's location at the convergence of multiple national highways and railway lines—including the Chennai–Kanyakumari and Villupuram–Pondicherry corridors—establishes it as a critical transportation junction for southern India. This geographic positioning profoundly impacts air quality through multiple pathways: proximity to the coast provides some moderating influence during monsoon seasons, yet the city's inland situation allows pollution to accumulate during dry periods. The surrounding agricultural landscape contributes seasonal biomass burning emissions, while the urban core experiences concentrated vehicular pollution at major intersections. The flat terrain inhibits natural dispersion of pollutants, particularly when combined with meteorological conditions common to this tropical region. Villupuram's role as a regional hub means diesel emissions from both road and rail transport permeate the airshed year-round, with construction dust adding to particulate loads as the city expands outward into former agricultural lands.

Villupuram's air quality follows a distinct seasonal rhythm shaped by its tropical wet-and-dry climate and regional agricultural practices. During the northeast monsoon season from October to December, increased humidity and occasional rainfall temporarily suppress particulate matter, though this period coincides with post-harvest agricultural residue burning that elevates PM2.5 levels. The winter months of November through February represent the peak pollution period, when cooler temperatures, reduced wind speeds, and frequent temperature inversions trap pollutants close to the surface. Morning fog often combines with smoke from biomass cooking and field burning, creating hazardous conditions particularly for respiratory patients and children. Sensitive groups should minimize outdoor activity during these months, especially in early mornings when inversion layers are strongest. The pre-monsoon period from March to May brings extreme heat and dry conditions that resuspend construction dust and road dust, though stronger daytime winds provide some dispersion. The southwest monsoon from June to September offers the cleanest air, with consistent rainfall washing pollutants from the atmosphere and winds dispersing local emissions. However, this period brings cyclone risks from the Bay of Bengal that can temporarily degrade air quality through transported dust and debris. For optimal outdoor activity, the late monsoon months of September and October generally provide the most favorable conditions, balancing reduced pollution with moderate temperatures before the winter inversion season begins.