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Arāk, situated in Iran's Markazi Province in West Asia, occupies a strategic position on the central Iranian plateau at an elevation of approximately 1,750 meters above sea level. This high-altitude city lies within a semi-arid basin surrounded by the Zagros Mountains to the west and the Karkas Mountains to the east, creating a topographical bowl that significantly influences its air quality. The urban area sits on relatively flat terrain with gentle slopes, facilitating urban expansion but also contributing to atmospheric stagnation. Arāk's location places it within Iran's industrial heartland, with proximity to major manufacturing zones and transportation corridors connecting Tehran to southwestern Iran. The city itself hosts industrial facilities including petrochemical plants, metalworks, and textile factories, while the surrounding region features agricultural lands producing grains and fruits. This creates a distinct urban-rural gradient where pollution sources concentrate in the city center while agricultural burning occasionally affects peripheral areas. The absence of major water bodies nearby—the nearest significant river being the Qareh Su, which is seasonal—means there's limited natural ventilation or humidity to disperse pollutants. The combination of industrial emissions, vehicular traffic in this growing city of over half a million people, and geographical confinement makes Arāk particularly vulnerable to air quality deterioration, especially during periods of atmospheric stability when pollutants become trapped in the valley-like setting.

Arāk's air quality follows distinct seasonal patterns shaped by its continental climate and geographical setting. During winter (December-February), cold temperatures and frequent temperature inversions trap pollutants close to the ground, creating persistent haze and fog that significantly degrade air quality—this period typically sees the worst pollution levels. Sensitive groups like children, elderly residents, and those with respiratory conditions should limit outdoor activities during these months, especially on calm, cold mornings when inversion layers are strongest. Spring (March-May) brings gradual improvement as increasing temperatures and occasional rainfall help disperse pollutants, though dust storms from surrounding arid lands can temporarily worsen conditions. Summer (June-August) offers relatively better air quality despite high temperatures, as thermal convection creates vertical mixing that disperses emissions, though ozone formation may increase on hot, sunny days. Autumn (September-November) sees a transitional period where cooling temperatures and reduced wind activity begin to recreate conditions favorable for pollution accumulation, particularly in late autumn. The city experiences minimal monsoon influence but does get occasional precipitation that temporarily clears the air. For health-conscious visitors and residents, late spring through early autumn generally provides the most favorable conditions for outdoor activities, while winter requires precautions like monitoring air quality indices and using masks during high-pollution episodes.