Early 2026 Weather Shifts Trigger Severe Rainfall and Cooling Across Southeast Brazil

São Paulo experienced a notable temperature decline, with highs barely surpassing 21°C and lows near 16°C on January 20 due to a retreating cold front coupled with persistent coastal moisture. These conditions caused overcast skies, light showers, and sustained humidity above 65%, prompting municipal authorities to maintain caution in vulnerable coastal areas where rainfalls remain intermittent but impactful. Earlier, on January 17, the city faced an extreme rainfall alert triggered by a powerful storm that flooded critical zones like Vila Prudente and Santo Amaro, with multiple incidents of motorists trapped by water. Approximately 46,000 households suffered power outages at peak impact, while emergency services responded to numerous calls for tree falls and flooding. Despite easing alerts by night, the event underscores the increasing intensity of convective storms in urban centers.

In the Rio de Janeiro metropolitan region, particularly in Duque de Caxias, rainfall accumulation exceeded 212 mm, prompting a maximum emergency alert. Floods inundated city centers, incapacitated traffic, and damaged public structures, leading to continuous monitoring by the local defense authorities and deployment of a multi-agency task force across Baixada Fluminense and adjacent municipalities. The forecast anticipates ongoing instability with moderate to strong showers, reinforced by nearby oceanic fronts and moderate winds, depressing temperatures to a range of 18°C–26°C.

At the broader regional scale, meteorological agencies identified two successive cold fronts advancing over the Brazilian coast initiating significant moisture inflows from the Amazon basin, intensifying the first ZCAS episode of the year. Rainfall totals in affected states such as Minas Gerais, Espírito Santo, and Rio de Janeiro could reach between 300 mm and 500 mm over a week, elevating flood and landslide risks notably in mountainous and urban areas. São Paulo state remains largely outside the primary ZCAS corridor, thereby avoiding heavy rains but continuing to face water scarcity challenges in reservoirs.

The National Meteorological Institute projects heterogeneous rainfall behavior for the agricultural sector: excess precipitation prevails in the North and parts of the South, favoring crops like soybean and maize, while the Southeast confronts drier-than-average conditions combined with higher evaporation rates, stressing water availability during critical crop phenological stages. This divergence necessitates targeted agricultural and resource management strategies amid shifting climate variability.

The persistent ZCAS event and related meteorological dynamics necessitate continuous government coordination through crisis management units to minimize impacts on urban mobility, energy infrastructure, and public safety. Market stakeholders in water-related utilities, agriculture, and infrastructure sectors should monitor evolving forecasts and adaptation measures closely.