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Yancheng occupies a distinctive position along China's central Jiangsu coast, where the Yellow Sea meets the fertile plains of the Yangtze River Delta. Situated at approximately 33.35°N latitude, this prefecture-level city spans a vast area characterized by flat alluvial terrain, with elevations rarely exceeding 5 meters above sea level, making it one of China's lowest-lying urban centers. Its extensive coastline—over 580 kilometers—and proximity to major waterways like the Sheyang River create a humid, maritime-influenced environment that paradoxically both disperses and traps pollutants. Yancheng lies within the Yangtze River Delta Economic Zone, a heavily industrialized region, yet maintains significant agricultural and ecological zones, including the renowned Yancheng Wetlands, a UNESCO World Heritage site that buffers some urban emissions. The city's urban core blends with sprawling suburban and rural landscapes, creating a complex urban–rural gradient where pollution sources vary from vehicular emissions and construction in dense districts to agricultural burning and fertilizer use in outlying areas. Its location downwind of major industrial hubs like Nanjing and Shanghai means it occasionally receives transboundary pollution, while local sources—including a growing manufacturing sector and port activities—compound air quality challenges. The flat topography inhibits natural ventilation, allowing pollutants to accumulate under stable atmospheric conditions, particularly when sea breezes weaken.

Yancheng's air quality follows a pronounced seasonal rhythm shaped by the East Asian monsoon, coastal meteorology, and local emissions. In winter (December–February), cold, stable conditions often lead to temperature inversions that trap pollutants near the ground, exacerbated by increased heating demand and occasional agricultural residue burning; this season typically sees the highest pollution levels, making outdoor activities less advisable, especially for sensitive groups like children and the elderly who should limit exposure. Spring (March–May) brings variable winds and occasional dust storms from northern China, but increasing precipitation helps cleanse the air, offering moderate improvement. Summer (June–August) features the southeast monsoon, with strong sea breezes and frequent rainfall that effectively disperse pollutants, resulting in the cleanest air of the year—ideal for outdoor pursuits, though high humidity can intensify ozone formation on hot days. Autumn (September–November) sees a gradual return to stable conditions as monsoon winds weaken, with pollution levels rising again due to reduced dispersion and increased industrial activity; fog events, common in late autumn, can further degrade visibility and air quality. Sensitive individuals should monitor forecasts closely during transitional months and consider wearing masks during peak pollution episodes, while all residents benefit from staying indoors during severe haze events.