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Nogales, Sonora, Mexico, occupies a strategic position in North America's borderlands, straddling the international boundary with Nogales, Arizona, USA, creating a unique binational urban corridor. Situated at approximately 31.3°N latitude and 110.93°W longitude, the city lies within the Sonoran Desert region at an elevation of around 1,200 meters (3,900 feet), nestled in the rugged terrain of the Sierra Madre Occidental foothills. This topography significantly influences air quality, as the surrounding mountains can trap pollutants in the valley basin, particularly during temperature inversions common in cooler months. Nogales' geography places it in a transitional zone between arid desert and higher-elevation woodlands, with limited proximity to major bodies of water—the nearest significant water source being the intermittent Santa Cruz River, which flows northward into Arizona. The urban character is shaped by its role as a major commercial gateway, with manufacturing, logistics, and cross-border trade driving economic activity, leading to vehicular emissions and industrial pollution from maquiladoras (assembly plants). Surrounding areas feature sparse vegetation typical of the Sonoran Desert, with some agricultural zones producing crops like pecans and grapes, though these are less dominant than urban-industrial sources. The urban-rural gradient is sharp, with the city center giving way rapidly to desert scrubland, but this does little to dilute pollution due to the basin-like setting that inhibits dispersion.

Nogales experiences distinct seasonal variations in air quality, driven by its desert climate and meteorological patterns. In winter (December to February), cooler temperatures often lead to temperature inversions, where a layer of warm air traps pollutants near the surface, causing peak pollution episodes; this is exacerbated by increased heating emissions and calm winds. Sensitive groups, such as those with respiratory conditions, should limit outdoor activities during these months, especially in the mornings when inversions are strongest. Spring (March to May) brings warmer temperatures and occasional winds that help disperse pollutants, making it a favorable time for outdoor activities, though dust storms from the surrounding desert can temporarily degrade air quality. Summer (June to August) is characterized by the North American Monsoon, which typically arrives in July, bringing afternoon thunderstorms that cleanse the air through rainfall and increased ventilation; however, high temperatures can increase ozone formation, particularly on hot, sunny days with low wind. Autumn (September to November) sees a return to drier conditions, with pollution levels generally moderate as temperatures cool and winds remain variable. Overall, the worst air quality tends to occur in winter due to inversions, while the monsoon season offers relief, making late spring to early summer a preferred window for outdoor pursuits, with health advisories emphasizing hydration and monitoring for dust or ozone alerts.