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Shanhu, located in Zhejiang Province of eastern China, occupies a distinctive position within the Yangtze River Delta region, approximately 29.6°N latitude and 120.8°E longitude. The city sits in a transitional zone between the coastal plains of eastern Zhejiang and the foothills of the Zhejiang-Fujian Highlands, creating a varied terrain that influences local air circulation patterns. At an elevation of roughly 50-100 meters above sea level, Shanhu benefits from some elevation advantages over completely flat urban areas, though its position in a basin-like formation surrounded by low hills can occasionally trap pollutants during stagnant weather conditions. The city lies about 40 kilometers inland from Hangzhou Bay, placing it close enough to maritime influences to receive moderating sea breezes, yet far enough to experience continental air mass effects. This proximity to water bodies—including the Cao'e River system that flows through the region—provides natural ventilation corridors when winds align properly. Shanhu exists within China's most economically dynamic industrial belt, surrounded by manufacturing zones, textile production facilities, and light industry that contribute to the 'general urban' pollution profile noted in available data. The urban-rural gradient shows dense urban cores transitioning to peri-urban industrial parks and then to agricultural lands producing tea, bamboo, and rice—a mix that creates complex emission sources including vehicle exhaust, industrial emissions, and occasional agricultural burning. The city's location in the densely populated Yangtze River Delta means it receives transported pollution from neighboring urban centers like Shaoxing and Hangzhou, particularly when prevailing winds blow from northwest to southeast during winter months.

Shanhu's air quality follows a distinct seasonal rhythm shaped by East Asian monsoon patterns and local meteorological conditions. During winter (December-February), cold, dry continental air masses from the northwest dominate, bringing stable atmospheric conditions that frequently cause temperature inversions—where warmer air aloft traps cooler, pollutant-laden air near the surface. These inversions, combined with increased heating demand and lower mixing heights, create the year's worst pollution episodes, particularly in January when industrial and residential coal combustion peaks. Sensitive groups like children, elderly residents, and those with respiratory conditions should limit prolonged outdoor exposure during these months and consider using air purifiers indoors. Spring (March-May) brings transitional weather with increasing rainfall and variable winds that help disperse pollutants, though occasional dust events from northern China can temporarily degrade air quality. The monsoon shift occurs in summer (June-August), when southeasterly maritime winds from the Pacific bring abundant rainfall and higher mixing heights that effectively scavenge pollutants from the atmosphere—making this the cleanest season for outdoor activities. However, high temperatures and humidity can combine with ozone precursors to create afternoon smog on stagnant days. Autumn (September-November) sees gradually deteriorating conditions as monsoon winds retreat and atmospheric stability increases, with October often marking the transition toward winter pollution patterns. The city's proximity to water bodies moderates some extremes but also contributes to radiation fog in cooler months, which can temporarily trap pollutants near the surface until daytime heating breaks the fog layer.