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Dehui occupies a strategic position in the fertile Songnen Plain of northeastern Jilin Province, approximately 80 kilometers northeast of Changchun, the provincial capital. Situated at coordinates 44.5350°N, 125.7030°E, this mid-sized city lies at an elevation of around 200 meters above sea level, characterized by gently undulating terrain that transitions from urban core to expansive agricultural hinterlands. The Yinma River flows through the region, though its influence on local air quality is minimal compared to larger water bodies. Dehui's location within China's Northeast Industrial Belt—proximate to major manufacturing centers in Changchun and Harbin—subjects it to regional pollution transport, particularly during prevailing northwesterly winds. The city itself functions as an agricultural processing hub amid vast corn and soybean fields, creating a distinct urban–rural gradient where seasonal burning of crop residues interacts with urban emissions from transportation and heating. This geography traps pollutants in the basin-like topography of the Songnen Plain, especially during temperature inversions common in the continental climate. The absence of significant mountain barriers to the west allows industrial plumes from upstream regions to accumulate, while the flat landscape offers little natural ventilation, making Dehui susceptible to prolonged pollution episodes despite its modest population of 839,786.

Dehui's air quality follows a pronounced seasonal rhythm dictated by its harsh continental climate and human activities. Winter (December–February) brings the worst pollution, as coal-fired heating systems operate at full capacity amid frequent temperature inversions that trap PM2.5 and sulfur dioxide near the ground; calm winds and heavy fog exacerbate these episodes, making outdoor activities risky for sensitive groups like asthmatics and the elderly. Spring (March–May) sees gradual improvement with increasing winds that disperse pollutants, though March remains problematic due to lingering heating needs and occasional dust storms from the arid west. Summer (June–August) offers the cleanest air, as monsoon rains from the southeast scrub the atmosphere, temperatures rise to prevent inversions, and agricultural burning is minimal; this is the ideal season for outdoor exercise. Autumn (September–November) marks a deterioration, particularly in October–November when farmers burn crop residues across the surrounding plains, combining with early heating emissions to create hazardous smog. Sensitive residents should monitor daily forecasts year-round, use air purifiers during peak months, and plan outdoor activities for summer afternoons when dispersion is optimal.