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Orūmīyeh, situated in Iran's West Azerbaijan province at coordinates 37.5439°N, 45.0647°E, occupies a strategic position in northwestern Iran near the borders with Turkey and Iraq. The city lies on the eastern shore of Lake Urmia, the largest saltwater lake in the Middle East, at an elevation of approximately 1,330 meters above sea level within a fertile plain surrounded by mountains. This basin-like topography creates a natural containment zone where air pollutants can accumulate, particularly during atmospheric inversions. The urban area, home to over 736,000 residents, serves as the provincial capital with mixed commercial, administrative, and residential functions, transitioning to agricultural hinterlands dominated by orchards, vineyards, and grain fields. Proximity to Lake Urmia introduces complex microclimatic influences—while the large water body can moderate temperatures, its shrinking size in recent decades has exposed extensive salt flats that contribute to particulate matter through wind erosion. The region lacks major heavy industrial belts but experiences pollution from urban sources including vehicle emissions, residential heating, and occasional agricultural burning. The urban-rural gradient shows decreasing pollution levels moving away from the city center toward the surrounding agricultural zones and mountains, though basin effects can trap pollutants across the wider region. This geographic setting makes Orūmīyeh particularly vulnerable to particulate matter accumulation, especially during stable atmospheric conditions common in colder months.

Orūmīyeh's air quality follows distinct seasonal patterns shaped by its continental climate and geographic basin. Winter (December-February) brings the worst pollution as cold temperatures increase residential heating demands—often using fossil fuels—while frequent temperature inversions trap pollutants near the surface. These stagnant conditions, combined with reduced wind speeds and occasional fog, create hazardous episodes where sensitive groups should limit outdoor exposure, particularly during morning hours. Spring (March-May) sees gradual improvement as increased precipitation helps cleanse the air and rising temperatures reduce heating needs, though late spring dust storms from dried lake beds and agricultural areas can cause temporary particulate spikes. Summer (June-August) offers the cleanest air with strong thermal convection dispersing pollutants, higher wind speeds, and minimal heating emissions, making this the optimal season for outdoor activities despite occasional heat-related ozone formation. Autumn (September-November) begins with relatively good conditions but deteriorates as temperatures drop, heating resumes, and atmospheric stability increases, with November often marking the transition to winter pollution patterns. Sensitive individuals—including those with respiratory or cardiovascular conditions, children, and the elderly—should monitor local air quality reports year-round, avoid strenuous outdoor activities during pollution episodes, and consider indoor air filtration during peak winter months when particulate concentrations are highest.