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Da'an is situated in the northwestern part of Jilin Province, China, positioned along the Songnen Plain where the Nen River and Songhua River converge, creating a distinctive fluvial landscape. This city lies at approximately 45.5°N latitude and 124.3°E longitude, placing it within the temperate continental monsoon climate zone of Northeast Asia, characterized by significant seasonal temperature variations. The terrain is predominantly flat with an average elevation of around 130 meters above sea level, which facilitates agricultural activities but also contributes to atmospheric stagnation under certain conditions. Da'an's location near the border with Inner Mongolia exposes it to dust storms originating from the Gobi Desert during spring, while its proximity to the Songhua River provides some moisture but limited air cleansing effects compared to coastal cities. The urban area is surrounded by extensive agricultural zones producing corn, soybeans, and rice, with agricultural burning occasionally contributing to particulate matter pollution. As a mid-sized city in China's northeastern industrial belt, Da'an experiences air quality influences from both local urban emissions and regional industrial activities in nearby cities like Baicheng and Qiqihar. The urban-rural gradient shows decreasing pollution levels moving away from the city center, though the flat terrain allows pollutants to disperse relatively evenly across the region when winds are favorable.

Da'an's air quality follows distinct seasonal patterns driven by its continental monsoon climate. During winter (December-February), severe cold temperatures frequently create temperature inversions that trap pollutants near the surface, compounded by increased residential heating emissions from coal and biomass burning. This season typically sees the highest pollution concentrations, making outdoor activities challenging, especially for sensitive groups like children, elderly, and those with respiratory conditions who should limit exposure. Spring (March-May) brings strong winds that disperse pollutants but also carry dust from the Gobi Desert, creating occasional spikes in particulate matter; late spring offers relatively cleaner air as temperatures rise and heating emissions decrease. Summer (June-August) features the most favorable air quality with frequent rainfall, higher atmospheric mixing heights, and prevailing southeasterly winds that bring cleaner air from the Pacific, making this the optimal season for outdoor activities. Autumn (September-November) begins with good air quality but deteriorates as temperatures drop, agricultural burning increases, and heating season commences, with October often showing transitional pollution levels. Sensitive groups should monitor air quality forecasts year-round, use air purifiers during high pollution periods, and schedule outdoor activities for summer mornings when pollution levels are typically lowest.