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Sihŭng, situated in the northwestern part of Gyeonggi Province, South Korea, occupies a strategic position within the Seoul Capital Area's southwestern periphery, approximately 25 kilometers from central Seoul. This satellite city lies on the relatively flat alluvial plains of the Han River basin, with an average elevation around 50 meters above sea level, creating a topographical setting that can trap pollutants under certain meteorological conditions. The city's urban character is defined by its role as a residential and light industrial hub within the broader Seoul metropolitan industrial belt, featuring mixed-use developments alongside manufacturing zones that contribute to local emissions. Sihŭng's location places it downwind from Seoul's major pollution sources during prevailing northwesterly winds, while its proximity to the Yellow Sea coastline, about 40 kilometers to the west, introduces marine influences that occasionally help disperse pollutants. The surrounding landscape transitions from dense urbanization in northern districts to more agricultural areas in southern fringes, creating an urban–rural gradient that affects pollution distribution. This geographical positioning within one of East Asia's most densely populated regions means Sihŭng experiences both locally generated pollution from transportation and industry, and regional transboundary pollution carried by winds from China's industrial northeast, particularly during spring. The city's terrain, lacking significant natural barriers, allows pollutants to accumulate during temperature inversions, especially in winter when cold air settles in the basin-like topography.

Sihŭng's air quality follows distinct seasonal patterns shaped by Korea's temperate monsoon climate. Winter months from December through February typically see the worst pollution episodes, as increased heating demands combine with frequent temperature inversions that trap pollutants near the ground, creating persistent haze; cold, stagnant air masses from the Asian continent bring both local emissions and transboundary pollutants. Spring, particularly March and April, brings another peak as strong westerly winds carry yellow dust from Mongolia and northern China, mixing with industrial emissions to create hazardous particulate matter concentrations. Sensitive groups should minimize outdoor activities during these spring dust events and winter inversion periods. Summer offers relief from June through August, when the East Asian monsoon brings cleaner maritime air from the south, with frequent rainfall effectively scrubbing pollutants from the atmosphere; this season presents the best conditions for outdoor activities despite occasional heat-related ozone formation on hot, sunny days. Autumn generally maintains moderate air quality through October, though November can see deteriorating conditions as heating season begins and winds shift to continental patterns. Throughout the year, morning fog in low-lying areas can temporarily worsen pollution visibility and concentration. Residents with respiratory conditions should monitor daily forecasts closely, use air purifiers during peak seasons, and schedule outdoor exercise for afternoons when mixing heights are typically higher.