Very strong El Niño raises alert for extreme weather in Brazil.

The September-October-November 2026 quarter begins under the prospect of a strong El Niño. According to estimates from the Climate Prediction Center (CPC) of the United States National Oceanic and Atmospheric Administration (NOAA), there is a 90% probability that the phenomenon will be very strong. This forecast is included in Bulletin No. 3 of the National Institute of Meteorology (Inmet) and partner institutions, which compiles monitoring of the phenomenon, climate projections, and potential impacts in Brazil.

According to the document, the Southern Region, especially Rio Grande do Sul, as well as areas of São Paulo and Mato Grosso do Sul, should register rainfall volumes above the historical average during the quarter. Conversely, the North and Northeast are more likely to face a drier period. The trend of below-normal rainfall also extends to areas of Central and Southeastern Brazil, particularly Mato Grosso, Tocantins, northern Goiás, Minas Gerais, and Espírito Santo.

Temperatures, in turn, are expected to remain above average across virtually the entire country. However, Inmet (the Brazilian National Institute of Meteorology) does not rule out the possibility of sharp temperature drops in September, associated with the arrival of cold air masses.

The combination of heat and prolonged drought in the Central and Northern regions also increases the risk of wildfires spreading. The bulletin warns that the situation could worsen if the start of the rainy season is delayed, a possibility considered likely for some areas.

Legal Amazon and Pantanal

In the Legal Amazon and the Pantanal, the September-October-November quarter normally corresponds to the transition period between the dry season and the beginning of the rains. This year, however, the influence of a more intense and prolonged El Niño may delay this change.

Projections from the Center for Management and Operation of the Amazon Protection System (Censipam) indicate below-average rainfall in Amapá, Roraima, Pará, Maranhão, Amazonas, and Acre, as well as northern Mato Grosso and areas in northern and central Tocantins and Rondônia. Temperatures are also expected to remain above average throughout the region.

The forecast indicates the possibility of prolonged drought conditions during part of the spring. As a result, soils and vegetation may remain drier for a longer period than usual, increasing vulnerability to the occurrence and spread of fire.

Monitoring will be essential.

NOAA researchers emphasize that more intense El Niño events do not necessarily mean more severe impacts. However, they increase the likelihood of extreme events associated with the phenomenon.

Given the predicted intensity of El Niño, Inmet reinforces the importance of continuous monitoring of meteorological conditions in the coming weeks. Assessment at different time scales will be crucial to identify in advance the areas most vulnerable to droughts, heat waves, and, at the opposite extreme, episodes of intense rainfall and flooding, especially in the Southern Region.

Bulletin No. 3 was prepared by Inmet in partnership with the Center for Weather Forecasting and Climate Studies (CPTec)/National Institute for Space Research (Inpe) and the Ceará Foundation for Meteorology and Water Resources (Funceme).