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Baisha is situated in Zhejiang Province's central-western region, approximately 150 kilometers southwest of Hangzhou, positioned within the Qiantang River basin where the Jinhua-Quzhou Basin transitions into the mountainous terrain of southwestern Zhejiang. The city occupies a valley landscape at an elevation of roughly 100-200 meters, surrounded by the Xianxia Mountains to the southwest and Dayang Mountain ranges to the northeast, creating a topographical bowl that influences local atmospheric conditions. Baisha lies along the upper reaches of the Wuxi River, a tributary of the Qiantang River system, with water bodies providing some humidity but limited dispersion effects due to the constrained valley geography. The urban core represents a mid-sized county-level city within China's Yangtze River Delta economic zone, exhibiting a distinct urban-rural gradient where dense central development gives way to agricultural peripheries specializing in tea plantations, bamboo forests, and citrus orchards. Industrial activity concentrates in designated zones along transportation corridors, featuring light manufacturing, textile processing, and building materials production typical of Zhejiang's interior cities. This geographical setting creates air quality challenges through temperature inversions that trap pollutants in the valley, limited wind corridors due to surrounding mountains, and the accumulation of both local emissions and regional transport from the more industrialized Hangzhou-Jinhua corridor to the northeast.

Baisha experiences distinct seasonal air quality patterns shaped by East Asian monsoons and local topography. Spring (March-May) brings variable conditions as winter's pollution accumulation gradually disperses with increasing rainfall and southeasterly winds, though temperature inversions still occur during clear nights, making late spring generally more favorable for outdoor activities. Summer (June-August) offers the cleanest air with frequent precipitation from the East Asian summer monsoon, strong convective mixing, and dominant southerly winds that efficiently ventilate the valley, though high humidity can combine with ozone precursors on hot days. Autumn (September-November) sees deteriorating conditions as monsoon retreats and stable high-pressure systems establish, creating frequent temperature inversions that trap pollutants in the valley basin, with October and November typically representing the annual pollution peak when agricultural burning occasionally supplements urban emissions. Winter (December-February) maintains poor air quality due to persistent temperature inversions, limited vertical mixing, and increased heating demand, though occasional cold fronts provide temporary relief. Sensitive groups should minimize outdoor exertion during autumn and winter mornings when inversion layers are strongest, favor summer and late spring for activities, and monitor local advisories particularly during autumn stagnation periods when the valley's topography maximizes pollution accumulation.