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Brno, the second-largest city in the Czech Republic, occupies a strategic position in the South Moravian Region, nestled within the basin formed by the confluence of the Svratka and Svitava rivers. Situated at approximately 49°N latitude and 16°E longitude, its coordinates place it in a transitional zone between the Bohemian Massif to the west and the Carpathian Mountains to the east, creating a sheltered valley that profoundly influences local air quality. The city's elevation ranges from 190 to 479 meters above sea level, with urban development concentrated in the lower basin areas, while surrounding hills like Špilberk and Kraví hora create natural barriers that can trap pollutants. Brno's geography features a mix of urban core, suburban districts, and nearby agricultural lands, particularly vineyards and farmland extending into the Moravian Karst region. Proximity to the Dyje River basin and several reservoirs, including Brno Reservoir, introduces moisture that can interact with emissions. The city lies within an industrial belt historically focused on machinery, textiles, and electronics, though deindustrialisation has reduced heavy manufacturing. Its position along major transport corridors, including highways connecting Prague to Vienna and Bratislava, contributes to vehicular emissions. The urban–rural gradient shows denser pollution in the central districts, with cleaner air in peripheral green spaces like Moravian Karst. This basin topography, combined with limited wind circulation, often leads to temperature inversions that exacerbate pollution episodes, particularly in colder months when heating emissions intensify.

Brno's air quality follows a distinct seasonal pattern shaped by its continental climate, with pollution peaks typically occurring in winter and troughs in summer. In winter (December to February), cold temperatures drive increased use of solid fuel heating, particularly in older residential areas, releasing particulate matter (PM2.5 and PM10). Temperature inversions are common in the basin, trapping pollutants near the ground, while low wind speeds from the northeast or southwest fail to disperse emissions. Sensitive groups, such as those with respiratory conditions, should limit outdoor activities during these months, especially on calm, foggy days. Spring (March to May) sees gradual improvement as heating demand decreases and more frequent winds from the west help clear the air, though pollen from surrounding agricultural areas can aggravate allergies. Summer (June to August) offers the best air quality, with higher temperatures reducing heating emissions and increased convective activity promoting pollutant dispersion; however, occasional heatwaves can elevate ground-level ozone, particularly in sunny, windless conditions. Autumn (September to November) brings a return to poorer air quality as temperatures drop and heating resumes, compounded by agricultural burning in rural outskirts and reduced precipitation. Throughout the year, weather hazards like fog and low cloud cover in the basin can worsen pollution visibility and health impacts. For optimal outdoor activity, plan visits in late spring to early autumn, avoiding prolonged exposure during winter stagnation events.