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Yanjiang, situated in the heart of Sichuan Province in southwestern China, occupies a strategic position along the Tuo River, a major tributary of the Yangtze River, at coordinates 30.1290°N, 104.6270°E. This urban district, part of the larger Ziyang prefecture-level city, lies within the Sichuan Basin, a vast sedimentary depression surrounded by mountainous terrain including the Longmen Mountains to the northwest and the Dalou Mountains to the south. The city's elevation averages approximately 350 meters above sea level, placing it within the basin's relatively low-lying interior where atmospheric conditions can trap pollutants. Yanjiang's geography positions it within the Chengdu-Chongqing economic zone, a major industrial and urban corridor in western China, contributing to regional pollution through manufacturing, transportation, and energy production. The surrounding landscape transitions from urban centers to agricultural zones, with rice paddies and vegetable farms dotting the rural periphery, creating an urban–rural gradient that influences local air quality through biomass burning and dust. Proximity to the Tuo River provides some moderating effects but also supports industrial activities along its banks. The basin's topography, characterized by encircling mountains, often leads to stagnant air masses, particularly during winter, exacerbating pollution accumulation from both local urban sources like vehicles and heating, and regional industrial emissions from nearby cities such as Chengdu and Chongqing.

In Yanjiang, air quality follows a distinct seasonal pattern shaped by the East Asian monsoon and the Sichuan Basin's unique meteorology. During winter (December to February), pollution peaks due to frequent temperature inversions that trap pollutants near the surface, compounded by increased emissions from residential heating and industrial activity. Cold, stagnant air and low wind speeds, often below 1 meter per second, hinder dispersion, making this period particularly hazardous for sensitive groups like children, the elderly, and those with respiratory conditions, who should limit outdoor exposure. Spring (March to May) brings gradual improvement as temperatures rise and monsoon winds begin to stir, though occasional dust storms from the northwest can temporarily degrade air quality. Summer (June to August) sees the lowest pollution levels, thanks to the southwest monsoon that delivers moist air and increased rainfall, which helps wash out particulate matter; this season is ideal for outdoor activities, with warm temperatures and clearer skies. Autumn (September to November) marks a transition, with pollution gradually increasing as monsoon winds weaken and atmospheric stability returns, leading to haze formation. Throughout the year, fog is common in the basin, especially in winter and autumn, often mixing with pollution to create smog. Sensitive individuals should monitor local air quality reports and consider using air purifiers indoors during peak months.