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Januária, nestled in the north of Minas Gerais, Brazil, occupies a unique geographic position within the São Francisco River Valley. Located at -15.4886 latitude and -44.3600 longitude, the city sits at an elevation of approximately 320 meters (1050 feet), contributing to a relatively warm climate. The surrounding landscape is characterised by the *cerrado* biome – a vast tropical savanna – interspersed with areas of *caatinga*, a semi-arid scrubland. The São Francisco River, a vital waterway for the region, flows nearby, influencing local humidity and potentially trapping pollutants during temperature inversions. Januária’s urban character is that of a regional hub, serving surrounding agricultural communities. The city’s economy is heavily reliant on agriculture, particularly cattle ranching and grain production, which can contribute to particulate matter from land use practices and seasonal burning. An increasing, though still limited, industrial presence along transport routes adds to potential emission sources. The urban-rural gradient is pronounced, with significant open land surrounding the city, but increasing deforestation and agricultural expansion are altering this balance. This interplay of natural features and human activity directly impacts Januária’s air quality, creating localized pollution hotspots and influencing dispersion patterns.

Januária experiences a distinct wet and dry season, rather than traditional four seasons. Air quality generally improves during the wet season (October to April) due to rainfall effectively scavenging particulate matter from the atmosphere. However, increased humidity can also foster mold growth, impacting respiratory health. The dry season (May to September) presents the greatest air quality challenges. Lower rainfall means pollutants accumulate, and agricultural burning for land preparation becomes prevalent, significantly elevating particulate matter levels. August and September are typically the worst months for air quality, coinciding with peak burning activity. Temperature inversions, common during the cooler, drier nights, trap pollutants near ground level, exacerbating the problem. Winds are generally light during the dry season, limiting dispersion. Sensitive groups – children, the elderly, and those with pre-existing respiratory conditions – should limit strenuous outdoor activity during these periods. The transition months, October and May, offer the most favourable conditions, with moderate temperatures and increasing/decreasing rainfall respectively. Monitoring wind direction is crucial, as pollutants can be transported from agricultural areas into the city.