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Tiruvannamalai, situated in the northern part of Tamil Nadu, India, occupies a distinctive position at the foothills of the Annamalai Hills, part of the Eastern Ghats mountain range. The city's geography is defined by its proximity to the sacred Arunachala Hill, a prominent granite outcrop that rises to about 800 meters, creating a natural amphitheater that influences local air circulation patterns. Located approximately 200 kilometers southwest of Chennai and 185 kilometers northwest of Puducherry, Tiruvannamalai lies in a transitional zone between the coastal plains of the Bay of Bengal and the drier interior plateau of the Deccan region. The terrain slopes gently from the hills toward the plains, with an average elevation of 170 meters above sea level, which affects temperature inversions during cooler months. The city is surrounded by agricultural zones dominated by paddy fields, sugarcane, and millet cultivation, interspersed with scrub forests. No major rivers flow through the urban core, though seasonal streams and tanks (artificial reservoirs) dot the landscape, contributing to humidity variations. Tiruvannamalai's urban character blends dense temple-centric development with sprawling peri-urban areas, creating an urban–rural gradient where biomass burning from household cooking and agricultural residue is common. This geography traps pollutants from vehicular emissions, temple incense, and construction dust, exacerbated by the bowl-like topography that limits dispersion, particularly during the dry season when winds are calm.

Tiruvannamalai's air quality follows a pronounced seasonal rhythm shaped by its tropical wet-and-dry climate. During the winter months from November to February, pollution peaks due to a combination of meteorological factors: cool temperatures lead to frequent temperature inversions that trap pollutants near the ground, while calm winds and morning fog reduce atmospheric mixing. This period coincides with peak pilgrimage activity for the Karthigai Deepam festival, amplifying vehicular emissions and incense from temple rituals. Sensitive groups, such as those with respiratory conditions, should avoid outdoor exertion in early mornings and evenings when pollution concentrations are highest. The summer season from March to May brings extreme heat, which can increase ozone formation from precursor pollutants, though stronger daytime winds provide some dispersion relief. The southwest monsoon from June to September offers the cleanest air, as heavy rainfall scrubs pollutants from the atmosphere and winds from the Arabian Sea enhance ventilation. However, occasional cyclones from the Bay of Bengal can stir up dust and debris. The post-monsoon period in October sees a gradual buildup of pollution as dry conditions return. For optimal outdoor activities, visit during the monsoon months when air quality is most favorable, and plan winter visits with precautions like wearing masks during peak hours.