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Siliguri, situated in West Bengal's northern reaches, occupies a strategically vital position as the gateway to India's Northeast and a crucial transit hub connecting mainland India with Bhutan, Nepal, and Bangladesh. The city sprawls across the narrow Siliguri Corridor, a mere 22-kilometer-wide strip of land flanked by Nepal to the west and Bangladesh to the east, with the mighty Teesta River flowing nearby. Its elevation of approximately 122 meters above sea level places it on the fringes of the Himalayan foothills, creating a unique urban-rural gradient where the city's dense commercial and residential zones transition rapidly into tea gardens and agricultural fields. This geography profoundly influences air quality: Siliguri's location in a valley-like basin surrounded by hills to the north and east traps pollutants, while its position as a major transportation nexus—with National Highway 31 and railway lines converging—generates significant vehicular emissions. The urban landscape, characterized by rapid, often unplanned growth, mixes industrial areas, bustling markets, and residential colonies, with brick kilns and small-scale manufacturing adding to the pollution load. Proximity to the Teesta River and numerous smaller water bodies provides some natural ventilation, but the city's role as an economic and logistical hub in a densely populated region means it constantly grapples with transboundary pollution, agricultural residue burning from surrounding farmlands, and localized urban sources, all exacerbated by its terrain that inhibits pollutant dispersion.

Siliguri's air quality follows a distinct seasonal rhythm shaped by the monsoon and regional weather patterns. In winter (December to February), pollution peaks as cold, stable air leads to frequent temperature inversions that trap pollutants near the ground, compounded by fog and calm winds; this season poses the highest risk, with sensitive groups like children, the elderly, and those with respiratory conditions advised to limit outdoor activities, especially during mornings and evenings. Spring (March to May) sees gradual improvement as temperatures rise and winds increase, though occasional dust storms from nearby arid regions can cause short-term spikes. The monsoon (June to September) brings relief, with heavy rains washing away pollutants and strong southwesterly winds dispersing emissions, making this the best time for outdoor pursuits. Post-monsoon (October to November) marks a transition, with decreasing rainfall and rising pollution as agricultural burning in surrounding areas intensifies, leading to hazy conditions. Throughout the year, Siliguri's proximity to the Himalayas influences local meteorology, with mountain-valley breezes sometimes aiding ventilation but also contributing to fog formation in cooler months. For health guidance, sensitive individuals should monitor local air quality reports, use masks during high-pollution periods, and plan activities for midday when dispersion is better, avoiding the winter peak altogether if possible.