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Hefei, the capital of Anhui Province in eastern China, occupies a strategic position at the heart of the Yangtze-Huaihe River Plain, approximately 130 kilometers west of Nanjing. Situated at coordinates 31.8206°N, 117.2273°E, the city lies at a modest elevation of 20-40 meters above sea level, creating a relatively flat urban basin that influences local atmospheric conditions. Hefei's geography is defined by its location between the Yangtze River to the south and the Huai River to the north, with the Chaohu Lake—China's fifth largest freshwater lake—positioned just southeast of the city center. This proximity to significant water bodies creates microclimates that can trap pollutants under certain meteorological conditions. The city serves as the economic and transportation hub of Anhui, positioned within the broader Yangtze River Delta economic zone, one of China's most industrialized regions. Urban expansion has created a distinct urban-rural gradient, with the metropolitan core surrounded by agricultural lands that transition to industrial zones along transportation corridors. The surrounding landscape features low hills to the west and northwest, while the eastern and southern approaches open to the expansive Yangtze River Plain. This topography, combined with the city's basin-like setting, contributes to atmospheric stagnation events that can exacerbate air pollution, particularly when regional air masses carry industrial emissions from neighboring provinces. The urban heat island effect further complicates local air circulation patterns, creating conditions where pollutants accumulate rather than disperse efficiently.

Hefei experiences distinct seasonal air quality patterns shaped by the East Asian monsoon system and its inland basin geography. During winter (December-February), cold, stable atmospheric conditions frequently create temperature inversions that trap pollutants near the surface, with heating demands from coal-fired systems adding to the pollution burden. January typically represents the peak pollution period, when reduced vertical mixing combines with increased emissions to create persistent haze episodes. Spring (March-May) brings transitional weather with increasing precipitation that helps cleanse the atmosphere, though dust storms from northern China can occasionally degrade air quality in March and April. The summer monsoon (June-August) introduces southeasterly winds from the Pacific that generally improve air quality through enhanced dispersion and rainfall scavenging, making July and August the cleanest months for outdoor activities. However, high temperatures and humidity can combine with ozone precursors to create photochemical smog on stagnant days. Autumn (September-November) sees gradually deteriorating conditions as monsoon winds retreat and atmospheric stability increases, with October and November often experiencing secondary pollution peaks. Sensitive groups including children, elderly residents, and those with respiratory conditions should limit prolonged outdoor exposure during winter pollution episodes and on days with visible haze. Morning hours typically show higher pollution concentrations due to overnight accumulation, making afternoon periods preferable for outdoor exercise. During summer, ozone-sensitive individuals should monitor midday conditions when photochemical activity peaks.