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Sumy, situated in northeastern Ukraine's Sumska Oblast, occupies a strategic position along the Psel River where the Central Russian Upland transitions to the Dnieper Lowland. This city of approximately 256,000 residents lies at coordinates 50.9119°N, 34.8028°E, placing it within the forest-steppe ecoregion characterized by mixed deciduous forests interspersed with agricultural plains. The urban core sits at an elevation of 166 meters above sea level, with gently rolling terrain that creates subtle microclimatic variations affecting pollution dispersion. Sumy's location approximately 350 kilometers northeast of Kyiv positions it within Ukraine's historical industrial belt, though its contemporary economy has diversified beyond traditional manufacturing. The Psel River, a tributary of the Dnieper, flows through the city center, providing some atmospheric moisture but insufficient to significantly mitigate particulate accumulation. Surrounding the urban area extends a gradient from dense residential districts to suburban zones and finally to expansive agricultural lands cultivating grains, sunflowers, and sugar beets. This rural-urban interface means seasonal agricultural burning occasionally contributes to particulate pollution, while the city's own emissions stem primarily from transportation, residential heating, and remaining industrial facilities. The region's continental climate, with limited natural ventilation corridors, allows pollutants to accumulate during atmospheric stagnation events, particularly when temperature inversions trap emissions in the shallow boundary layer. Sumy's geographic position away from major mountain ranges means it lacks natural wind channels that could regularly flush pollutants, making local emission control particularly important for air quality management.

Sumy experiences distinct seasonal air quality patterns shaped by its continental climate. During winter (December-February), cold temperatures increase residential heating demands, primarily through natural gas but with some coal and biomass use in outlying areas, elevating particulate matter concentrations. Temperature inversions frequently occur as cold, dense air settles in the Psel River valley, trapping pollutants near ground level. These stagnant conditions create the year's poorest air quality, particularly during windless periods in January. Sensitive groups should limit prolonged outdoor exertion on calm winter days. Spring (March-May) brings gradual improvement as heating demands decrease and increased atmospheric mixing disperses pollutants. However, March can still experience poor air quality when lingering cold combines with agricultural field preparation activities. Summer (June-August) offers the cleanest air with good ventilation, though occasional heat waves in July and August can elevate ground-level ozone precursors from transportation emissions. Autumn (September-November) sees a gradual deterioration as temperatures drop and heating begins, compounded by agricultural residue burning in October. November often marks the transition to winter stagnation patterns. For optimal outdoor activity timing, late spring through early autumn provides the most favorable conditions, while January and February present the greatest challenges. Those with respiratory conditions should monitor local air quality reports during heating season inversions and consider indoor air filtration during prolonged stagnant periods.