The Brazilian state of São Paulo has recorded its heaviest September rainfall in more than 80 years, an effect of the El Niño climate phenomenon that meteorologists say is only the beginning of a more intense pattern of disasters expected by the end of the year, when the event is due to reach its peak.
On Monday, September 14, 2026, the state capital, São Paulo, logged 253.8 millimeters of rain, making it the rainiest September the city has recorded in over eight decades.
The storms have also caused damage across several regions of the state, leaving two people dead and one person missing since the previous weekend. The city of Eldorado, in the Vale do Ribeira region, was left completely underwater.
El Niño is considered one of the strongest such events in decades and could affect the planet's climate in ways that last until 2027, according to the report.
Unstable Weather to Continue in South and Center-West
The Southeast is not the only region where El Niño is expected to keep shaping the weather. In the coming months, unstable conditions are also likely to persist across parts of southern and central-western Brazil, according to meteorologist Alexandre Nascimento, a partner and director at the forecasting firm Nottus Meteorologia.
Nascimento said El Niño is indeed linked to these events. He explained that the phenomenon normally brings above-average rainfall to southern Brazil, but the affected area can shift further north to reach parts of the Southeast and Center-West. He noted that the regions hit hardest in September, between the states of Paraná and São Paulo, are likely to remain the most affected in the coming weeks and months.
Rain Raises Risk of Flooding and Landslides
The repeated rounds of El Niño-driven rain can further destabilize soil and increase the vulnerability of regions that already face a risk of flooding and landslides.
Nascimento said another pattern occurring frequently is strong wind gusts as cold fronts arrive, and that this is expected to continue in the coming months in both the South and Southeast. He added that extremely high temperatures are expected mainly in the northern parts of the Southeast and Center-West, as well as in the North and Northeast.
Phenomenon Could Reach Historic Levels
In August, the global average daily sea surface temperature reached 21.1 degrees Celsius, a historic record and the highest level of ocean heat ever measured, surpassing the previous mark of 21.09 degrees Celsius set in March 2024.
According to the European Centre for Medium-Range Weather Forecasts and Copernicus, the European Union's Earth observation program, the rise is being driven in part by the warming associated with El Niño.
Persistently rising temperatures carry major consequences for ecosystems and increase risks for coastal communities and low-lying island nations. In Brazil, this is why areas closer to the coast are experiencing storm surges and strong winds, and Nascimento said disasters in those regions will continue to intensify.
Nascimento said the phenomenon is already considered very strong and will keep warming, potentially reaching historic and record levels in the coming months. He said that pattern, tied to temperature conditions in the central equatorial Pacific, is what defines the event.
What Is El Niño?
El Niño occurs when the waters of the Pacific Ocean warm above normal levels, altering wind circulation and rainfall patterns. The process affects the entire planet, though its impact varies across Brazil's regions, ranging from heavy rain and flooding to severe drought and water shortages in reservoirs.
Winds over the Pacific normally blow from east to west, pushing warm water from the Americas toward Oceania and Indonesia and keeping the waters near South America relatively cool. During El Niño, rising Pacific temperatures disrupt the balance between wind, pressure and humidity. Evaporation increases, winds weaken, and the warm water that usually sits near Oceania spreads back toward South America, unsettling weather patterns on a global scale.
