Super El Niño Drought Threatens Amazon Rain and Brazilian Power

A Super El Niño Amazon drought is already under way, and Met Office maps now show a dangerously dry anomaly over the basin by January 2027. Tim Li at the University of Hawaii says June to August rainfall was already weaker than in previous large El Niños, while the Pacific event was still gathering.

The first-order story is fire in a forest near a climate threshold. The delayed hit is plainer. Less rain means less water for Brazil’s dams, less moisture riding south as flying rivers, and another carbon pulse from trees that keep dying for years after the flames go out.

A Terribly Dangerous Rainfall Anomaly by January

Adam Scaife, head of long range forecasting at the Met Office, says very strong El Niños tend to pile their heat close to the coast of South America, which sharpens drought over the Amazon. The service’s latest seasonal maps, he said on 7 September 2026, show a “terribly dangerous [rainfall] anomaly” over the basin by January, with hotter air sitting on top of the dry spell.

I have never seen an El Niño signal this intense in our forecasts. A typical El Niño leads to an equatorial Pacific sea-surface temperature rise of between 1-2 degrees, with 2 o C being a really big event.

Adam Scaife, Head of Long Range Forecasting, Met Office, 24 August 2026 briefing

That 24 August briefing also published forecasts of more than 3°C in the Niño 3.4 region in the coming months. Scaife said that if those runs hold, 2026 will far exceed recent El Niño experience and its worldwide climate effects. Tropical South America sits on the dry side of that pattern, with Central America and the western Pacific.

Li’s reading of the Amazon summer matches that track. “The rainfall anomaly in this year, 2026, in the summertime, is already much stronger than all other events,” he said. “In the Amazon you already see drought.” If this year follows earlier large El Niños, he added, that dry pattern will intensify into the coming months.

Pacific Heat Is Piling Up Off South America’s Coast

NOAA’s Climate Prediction Center, in its 31 August 2026 briefing, kept an El Niño Advisory in force. Equatorial waters were above average across the east-central and eastern Pacific, and the atmosphere over the equator already matched an El Niño circulation. The eastern coastal index, Niño 1+2, stood at 3.5°C on the weekly chart, the patch of ocean Scaife says funnels heat toward South America.

THE CPC WINTER ODDS

• Very strong: Greater than 90 percent chance during September-November through November-January 2026-27.
• Historic peak: A 69 percent chance of a historic event in October-December 2026, stronger than any El Niño in the post-1950 record.
• How long: The event is expected to persist through Northern Hemisphere spring 2027.
• Relative index: The May-July 2026 Relative Oceanic Niño Index was 1.0°C and still climbing.

Above-average sea-surface temperatures first showed up in the far eastern equatorial Pacific in early February 2026 and generally increased across the east-central and eastern Pacific from mid-April. That eastern bias is why Amazon drought is the regional tell, not a side effect. Nick Dunstone at the Met Office also warned that large El Niños dump ocean heat into the air, so 2027 is very likely to replace 2024 as the warmest year on record and to exceed 1.5°C above the preindustrial period for another calendar year.

495 Million Tonnes Came From Just 1 Percent of the Forest

The last comparable Pacific spike, in 2015-16, left a bill the Amazon was still paying three years later. A team led from the University of Oxford and Lancaster University tracked every stem in plots across Brazil’s Lower Tapajós, an eastern Amazon belt of about 6.5 million hectares, then scaled the deaths. In that strip, which is 1.2 percent of the Brazilian Amazon and 1 percent of the whole biome, 2.5 billion stems died and the pulse emitted 495 million tonnes of CO2.

THE LOWER TAPAJÓS BILL, 2015-16

• Small stems: About 2.5 billion plants under 10 centimetres in diameter died, plus about 447 million larger trees.
• How long deaths ran: Mortality stayed above the pre-event baseline for 36 months in drought-hit forest and 30 months in forest that also burned.
• The fire multiplier: Carbon from burned, human-modified forest was almost six times the loss from drought alone.
• The recovery gap: Three years on, growth and new stems had offset only 37 percent of those emissions.

Erika Berenguer, who led the field counts, and her colleagues were still watching trees die long after the El Niño itself had faded. The 495 million tonnes from that one strip exceeded a full year of deforestation emissions across the Amazon. Li’s feedback is the same engine in hotter form: less rain, less evaporation, higher air temperature, then fire in forest that is not built to burn.

Brazil Still Draws 51 Percent of Its Power From Rivers

When Amazon rain fails, the loss shows up in turbine halls months later. Coupled biosphere and hydrology modelling of 2015-16 found the basin received 220 to 390 millimetres less rain, 13 to 22 percent below average, between September 2015 and May 2016. River discharge ran 40 percent below average from December 2015 to February 2016. At Óbidos, the last gauge on the main stem, the October-April shortfall was 1,100 cubic kilometres, a 25 percent cut.

Brazil still leans on that water. The Energy Research Office’s 2026 summary for 2025 found hydropower supplied 51.2 percent of Brazil’s electricity, even after a 4.8 percent drop in hydro generation from 2024. Full reservoirs in the north can hide the lag. Tucuruí was around 95 percent full in mid-June 2026 after a wet end to 2025. In 2015 the rain failed in September and the rivers did not crash until the turn of the year, then stayed low into the following dry season.

Operators are already treating this dry season as a shortage. On 26 August 2026, regulators let Norte Energia, which runs the Belo Monte plant on the Xingu, cut the flow through the 119-square-kilometre intermediate reservoir from a 300 cubic metres per second minimum to 100 cubic metres per second, a third of the previous floor, through 30 November. The Volta Grande bend downstream is fishing ground, transport, and drinking water for Indigenous and riverine communities. A dam that needs drought waivers before the Pacific event has even peaked is not a spare battery. It is a second-order claim on a shrinking river.

How Much Rain Does the Forest Still Make for Itself?

Trees in the Amazon send up to half the rain that falls on the western basin back into the air, so a drought in one region can starve another hundreds of kilometres downwind. That recycled vapour is the flying-river supply for farms and cities on the far side of the forest. When the canopy thins, the pump weakens, and São Paulo has already lived through the result: the Cantareira system that feeds the city fell to 5 percent in January 2015.

Antonio Nobre, a climatologist at Brazil’s National Institute for Space Research, has long described the forest as a biotic pump. Follow a water molecule, he has said, and most of the clouds over São Paulo have crossed the Amazon. Arie Staal, an assistant professor at Utrecht University and a co-author of the May 2026 Nature study on Amazon drying, put the same physics in network terms. When deforestation cuts moisture transport in one area, entire regions hundreds or even thousands of kilometres away can lose resilience through cascading drought.

Deforestation makes the Amazon far less resilient than we previously anticipated. It dries out the atmosphere and weakens the forest’s own rainfall generation.

Nico Wunderling, scientist, Potsdam Institute for Climate Impact Research

That is why a Pacific forecast over the Amazon is also a rainfall forecast for places that never see the river. The forest is not only the victim of this El Niño. It is the machine that still has to manufacture part of the wet season while the Pacific is suppressing the rest.

Wunderling’s Model Puts Dieback Within Reach of 1.5°C

Nico Wunderling and colleagues at the Potsdam Institute for Climate Impact Research published the threshold math on 6 May 2026. Without extra clearing, their moisture-tracking model keeps most of the Amazon stable until global warming hits 3.7 to 4.0°C, and even then up to a third of the forest is at risk. Add deforestation, and the floor falls. At a 1.5 to 1.9°C warming threshold combined with 22 to 28 percent forest loss, 62 to 77 percent of the Amazon shifts toward degraded woodland or savannah-like cover.

AMAZON DIEBACK THRESHOLDS IN THE PIK MODEL

The world is already close to 1.5°C. The Amazon is already 17 to 18 percent gone. Most of the simulated collapse in the model is not a local clear-cut. It is a knock-on drought that travels hundreds to thousands of kilometres once moisture recycling fails. Johan Rockström, PIK’s director and a co-author, said continued clearing is undermining the forest’s role as a carbon sink and a rainfall regulator, with effects that would not stay inside the basin.

Bernardo M. Flores, an ecology researcher at the University of Santiago de Compostela and a co-author, has said the paper still undercounts fire. Depending on how much of the rainforest burns in the current El Niño, he said, “it could basically cross the tipping point.” He also said the system may have crossed already. “We don’t know.”

The Dry Season Is Arriving Before the Last Drought Healed

This El Niño is not landing on a rested forest. The 2023-24 drought was already the harshest on record in parts of the basin, and plots that burned then were still losing trees years after 2015-16. Canopy chemistry work after that last extreme found trees pumping out stress compounds, including volatiles never recorded in Amazon air, for weeks into the following wet season. A forest still in recovery is a forest that lights easier when the next dry anomaly arrives.

THE ROAD TO JANUARY

1. Early February 2026: Above-average sea-surface temperatures emerge in the far eastern equatorial Pacific.
2. Mid-April 2026: Warm anomalies increase across the east-central and eastern Pacific.
3. June-August 2026: Amazon rainfall runs well below average, stronger than prior large El Niños at the same stage, Li says.
4. 13 August 2026: CPC puts a greater than 90 percent chance on a very strong event through winter, and 69 percent on a historic October-December peak.
5. 24 August 2026: Scaife calls the forecast signal the most intense he has seen; Dunstone flags 2027 as likely the hottest year.
6. 26 August 2026: Belo Monte is allowed to cut Xingu flow to 100 cubic metres per second through 30 November.
7. January 2027: Met Office rainfall maps show the dangerous Amazon dry anomaly; El Niño is still expected to last into spring.

WHAT WE KNOW

• The Pacific event: It is already strong, eastern-weighted, and more likely than not to beat the post-1950 record this winter.
• The Amazon summer: June to August 2026 rain was already drier than in previous large El Niños, with hotter air on top.
• The last analogue: In 2015-16, 1 percent of the biome produced 495 million tonnes of CO2 and rivers ran 40 percent low by midsummer.

WHAT IS UNCONFIRMED

• A basin-wide flip: Flores says a single fire season could cross the threshold, and also says it may have crossed already. The PIK numbers are a range, not a date.
• January totals: The Met Office anomaly is a forecast, not a gauge reading. River levels and fire counts for late 2026 are still being written.
• Power rationing: Northern reservoirs started the dry season high. Whether Belo Monte’s waiver becomes a system-wide hydro crunch depends on rain that has not fallen yet.

CPC still expects El Niño to last through spring 2027, so the Amazon dry anomaly is not a January spike that then lets go. The forest will be asked to recycle rain, feed the Xingu, and hold carbon through a Pacific event Scaife says is stronger than any signal in his forecast archive, after a summer that Li says was already the driest El Niño start on his books.