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Ch'ŏnan, situated in South Korea's Chungnam province, occupies a strategic position within the broader Seoul Capital Area's southern periphery, approximately 80 kilometres south of Seoul. This location places it within the country's industrial heartland, where urban expansion meets agricultural plains, creating a distinct urban–rural gradient that significantly influences air quality. The city lies on relatively flat terrain at an elevation around 20–30 metres above sea level, nestled between the low-lying coastal plains to the west and the modest foothills of the Sobaek Mountains to the east. Proximity to the Yellow Sea, about 30 kilometres to the west, introduces marine influences that can alternately disperse or trap pollutants depending on wind patterns. Ch'ŏnan's geography positions it within South Korea's central industrial belt, with manufacturing zones and transportation corridors contributing to general urban pollution sources. The surrounding landscape—a mix of rice paddies, orchards, and urban sprawl—creates complex airshed dynamics where agricultural emissions occasionally interact with urban pollutants. Its location in a basin-like formation, though not pronounced, can foster temperature inversions that trap particulate matter and gases, exacerbating pollution episodes. The city's growth as a residential and industrial hub, coupled with its position downwind from larger metropolitan areas during certain weather patterns, means it experiences both locally generated pollution and regional transport of contaminants from the greater Seoul metropolitan region.

Ch'ŏnan's air quality follows a distinct seasonal rhythm shaped by East Asian monsoonal patterns and local meteorological conditions. During winter (December–February), pollution typically peaks due to increased heating emissions, frequent temperature inversions that trap pollutants near the surface, and occasional transport of dust and industrial haze from northern China via northwesterly winds. Sensitive groups should limit prolonged outdoor exposure during these months, especially on calm, cold days when inversion layers are strongest. Spring (March–May) brings variable conditions: early spring may still experience pollution episodes from continental dust storms (yellow dust), while later spring sees improving air quality as increased ventilation from seasonal winds and precipitation help disperse pollutants. Summer (June–August) generally offers the cleanest air, with the East Asian monsoon bringing southerly winds from the Yellow Sea that flush out contaminants, though occasional high ozone levels can occur on hot, sunny days. Autumn (September–November) presents a transitional period where decreasing temperatures and shifting wind patterns may lead to gradual pollution buildup, particularly in late autumn as heating season begins. For optimal outdoor activity, late spring through early autumn provides the most favourable conditions, while winter months require caution, especially for children, elderly, and those with respiratory conditions who should monitor air quality forecasts and consider indoor air purification during peak episodes.