Vigo, Spain's most populous city in Galicia, occupies a dramatic geographic position that profoundly influences its air quality. Nestled along the southern shore of the Ría de Vigo—one of Galicia's iconic coastal inlets—the city is cradled by the Serra do Galiñeiro mountains to the east, creating a natural amphitheater that traps urban emissions. This unique topography, with elevations ranging from sea level to over 600 meters in nearby peaks, creates microclimates and ventilation challenges. Vigo's urban character blends dense historic quarters with sprawling industrial zones along its port, one of Europe's busiest fishing and commercial harbors, which contributes maritime and port-related emissions. The city sits within the Atlantic Arc urban corridor, with a distinct urban-rural gradient transitioning rapidly from metropolitan density to the forested hills and agricultural valleys of inland Galicia. Proximity to the Atlantic Ocean moderates temperatures but also brings humid air that can interact with pollutants. The surrounding landscape—a mix of coastal wetlands, eucalyptus plantations, and small-scale farming—creates biogenic emissions that mix with urban pollution. Vigo's position at the mouth of the ría means sea breezes can disperse pollutants, but during calm conditions, the mountain barriers lead to accumulation, particularly in the city's lower-lying areas. This geographic setting makes air quality highly variable, influenced by both local urban activities and regional atmospheric patterns.

Vigo's air quality follows a distinct seasonal rhythm shaped by its Atlantic climate and urban geography. In winter, from December to February, cooler temperatures and frequent thermal inversions in the mountain-ringed basin trap pollutants near the surface, leading to higher particulate matter levels, especially during calm, foggy mornings—residents with respiratory conditions should limit outdoor exertion during these periods. Spring, from March to May, brings increased rainfall and stronger westerly winds from the ocean, which effectively disperse pollutants, making this an excellent season for outdoor activities; however, occasional Saharan dust intrusions can temporarily degrade air quality. Summer, from June to August, sees lower pollution overall due to consistent sea breezes and vacation-related reductions in traffic, though ozone levels may peak on hot, sunny days when sunlight reacts with nitrogen oxides from vehicles and port operations—sensitive groups should avoid midday outdoor exercise during heatwaves. Autumn, from September to November, marks a transition with returning traffic and industrial activity, combined with more frequent stagnant weather patterns as the Atlantic storms lessen, leading to gradual pollutant buildup; this season requires monitoring for those with cardiovascular issues. Throughout the year, Vigo's air quality is best after rainfall or during windy conditions, with the most favorable months for outdoor pursuits typically being May, June, and September.