Yongcheng, situated in eastern Henan province at coordinates 33.9299°N, 116.4500°E, occupies a strategic position in China's North China Plain, approximately 300 kilometers southeast of Zhengzhou, the provincial capital. This prefecture-level city lies within the Huang-Huai-Hai Plain, characterized by flat to gently undulating terrain with an average elevation of around 40 meters above sea level, creating a basin-like topography that traps atmospheric pollutants. Yongcheng's location places it at the convergence of several major transportation corridors, including the Longhai Railway and multiple highways, fostering urban-industrial development amidst surrounding agricultural zones. The city is part of the broader Central Plains economic region, with proximity to the Huai River basin to the south, though no major water bodies directly border the urban core. This geography creates a distinct urban-rural gradient where the compact city center transitions rapidly to extensive farmland, primarily cultivating wheat and corn. The flat landscape, combined with the city's position downwind from industrial areas in neighboring provinces during certain wind patterns, exacerbates air quality challenges. Particulate matter accumulates readily due to limited natural ventilation, while agricultural burning in surrounding rural areas periodically contributes to pollution episodes. The urban heat island effect further intensifies local pollution retention, making Yongcheng's air quality particularly sensitive to meteorological conditions.

Yongcheng experiences distinct seasonal air quality patterns shaped by its continental monsoon climate. In winter (December-February), cold, stagnant conditions prevail with frequent temperature inversions that trap pollutants near the surface, compounded by increased coal burning for heating. This season typically sees the highest pollution levels, particularly in January, when sensitive groups like children, elderly, and those with respiratory conditions should limit prolonged outdoor exposure. Spring (March-May) brings variable conditions: March often remains polluted due to lingering winter patterns and occasional dust storms from northern regions, but conditions gradually improve by May as temperatures rise and ventilation increases. Summer (June-August) offers the cleanest air, with the East Asian monsoon bringing southeasterly winds that disperse pollutants, though high temperatures can occasionally elevate ozone levels during afternoon hours. Autumn (September-November) begins with relatively good air quality in September but deteriorates through October and November as temperatures drop, atmospheric stability increases, and agricultural burning occurs after harvests. Throughout the year, calm wind days and foggy conditions, most common in late autumn and winter, significantly worsen pollution by reducing dispersion. For optimal outdoor activity timing, late spring through early autumn provides the most favorable conditions, while winter months require caution and monitoring of daily air quality forecasts.