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Jundiaí occupies a strategic position in southeastern Brazil's São Paulo state, nestled within the Serra do Japi mountain range at an elevation of approximately 762 meters above sea level. This mid-sized city of 401,896 residents sits 60 kilometers northwest of São Paulo metropolis, placing it within the influential orbit of Latin America's largest urban-industrial complex while maintaining its own distinct character. The terrain transitions from the Atlantic Forest remnants of Serra do Japi's protected slopes to the urbanized valley floor where the city center developed, creating a pronounced urban-rural gradient that significantly influences local air quality patterns. Jundiaí's location in the Tietê River basin positions it within an important hydrological network, though the city itself is more directly influenced by smaller tributaries like the Jundiaí-Mirim River. The surrounding landscape combines agricultural zones—notably vineyards and fruit orchards benefiting from the region's microclimate—with industrial districts that developed along transportation corridors connecting São Paulo to interior markets. This geographic setting creates a complex air quality dynamic where pollutants from local vehicle emissions and occasional industrial activity can become trapped against the mountain slopes during atmospheric inversions, while the city's elevation generally provides better ventilation than the heavily polluted São Paulo basin to the southeast. The urban expansion into former agricultural areas has created a patchwork of land uses that alternately contribute to or mitigate pollution through vegetation cover and heat island effects.

Jundiaí experiences distinct seasonal air quality variations shaped by its subtropical highland climate, with pollution patterns following both meteorological cycles and human activity rhythms. During summer (December-February), increased rainfall from convective afternoon thunderstorms effectively scrubs particulate matter from the atmosphere, making this the cleanest period for outdoor activities despite occasional ozone formation on hot, stagnant days. Autumn (March-May) brings transitional conditions with decreasing precipitation and more frequent temperature inversions that can trap pollutants overnight, particularly vehicle emissions during morning rush hours. Winter (June-August) represents the most challenging season for air quality, with dry conditions, persistent high-pressure systems, and frequent radiation inversions that concentrate pollutants near the surface, especially fine particulate matter from increased biomass burning in surrounding agricultural areas and residential heating. Sensitive groups should limit prolonged outdoor exposure during winter mornings when inversion layers are strongest. Spring (September-November) shows gradual improvement as increasing rainfall returns and ventilation patterns shift, though occasional dust from agricultural preparation and construction activity can cause short-term spikes. The city's position in the Serra do Japi foothills creates localized wind patterns that sometimes funnel pollutants from the São Paulo metropolitan region northwestward, particularly during winter when prevailing winds shift. Residents with respiratory conditions should monitor daily conditions most carefully during the dry winter months and consider indoor air purification during prolonged inversion events.