El Niño 2026 tracks record 1997 event, NASA sea-level maps show

Key takeaways

• NASA sea-level maps published on 23 October 2026 show the El Niño 2026 pattern in the Pacific closely resembles the record 1997-98 event, with warm, raised water stretching all the way to South America.
• NOAA's Climate Prediction Center (CPC) said on 8 October that a strong-to-very-strong El Niño is likely through January-March 2027, with odds remaining above 83%.
• CPC put the Niño-3.4 index at +2.1°C and the far-eastern Niño-1+2 region at +3.9°C, with surface anomalies above +4°C in parts of the eastern Pacific.
• CPC gives an 83% chance that October-December 2026 reaches a "historic" level (a three-month relative index of +2.5°C or more), above the +2.3°C peaks of both 1997-98 and 2015-16 on that index.
• Strong El Niño years have historically brought floods to Peru and the southern United States and drought to Indonesia, eastern Australia and southern Africa, but forecasters stress these are tendencies, not guarantees.

El Niño 2026: what NASA's satellite comparison shows

El Niño 2026 closely resembles the record 1997-98 event: NASA sea-level maps released on 23 October show this October's Pacific pattern matching October 1997, with warm water reaching South America. NOAA gives strong-to-very-strong odds above 83% through January-March 2027.

The comparison comes from NASA Earth Observatory, which set a Sentinel-6 Michael Freilich map from 12 October 2026 beside a TOPEX/Poseidon map from 13 October 1997. A third panel adds a Jason-2 map from 12 October 2015, the last time a comparable event built in the Pacific.

The three satellites belong to the same family of radar altimeters. NASA describes the result as a 35-year record collected from nearly identical instruments flying almost the same ground track, which is what makes a like-for-like comparison across three decades possible.

Why sea level is a good El Niño signal

Warm water expands, so a warmer ocean stands slightly higher. During El Niño, the trade winds that normally pile warm water up in the western Pacific weaken, and that warm pool sloshes east. Altimeters see it as a band of higher-than-normal sea surface height along the equator.

In both the 1997 and 2026 maps, that raised band runs across the central and eastern equatorial Pacific and reaches the coast of South America. In the 2015 map, the elevated water stayed farther offshore and did not reach the coast to the same extent, according to NASA.

Josh Willis, project scientist for sea level missions at NASA's Jet Propulsion Laboratory, told NASA Earth Observatory that the 2026 event resembles 1997 in its sea-level tilt and in warm water reaching South America, so its impacts could be similar. He added that this year's event appears on track to be even bigger than 1997, and that it developed much more suddenly.

Willis also urged caution. "The search for the 'typical' El Niño is very elusive," he said, noting that each event differs in where its effects land.

What NOAA's latest El Niño outlook says

NOAA's Climate Prediction Center keeps an El Niño Advisory in place. Its 8 October 2026 ENSO diagnostic discussion said El Niño "continues to strengthen" and that a strong-to-very-strong event is likely through January-March 2027, with a chance that remains above 83%.

The ocean readings behind that call are large. CPC reported sea surface temperature anomalies of +2.1°C in the Niño-3.4 region, the main index used to measure El Niño, +3.0°C in Niño-3 and +3.9°C in Niño-1+2 off Peru and Ecuador. Below the surface, CPC said temperatures at depth in the eastern Pacific were more than 10°C above average.

The atmosphere is responding as well. CPC noted enhanced rainfall from the central to eastern Pacific, suppressed rainfall over Indonesia, and significantly negative Southern Oscillation indices, all classic signs of a coupled El Niño.

The World Meteorological Organization (WMO) points the same way. Its seasonal update published on 3 September 2026 said multi-model forecasts pointed to further strengthening, with a September-November Niño-3.4 anomaly of about 3.6°C and a peak in November-December. WMO also expects a positive Indian Ocean Dipole, which can add to dryness around Indonesia and Australia.

How NOAA now measures strength

NOAA now uses the Relative Oceanic Niño Index (RONI) for official ENSO monitoring. RONI compares the tropical Pacific with the rest of the tropical oceans, which removes part of the background warming trend. That is why a single season can look stronger on the traditional Oceanic Niño Index (ONI) than on RONI.

CPC defines a "historic" event as a three-month RONI of +2.5°C or more. Its 8 October discussion gave the odds of reaching that level as 54% for September-November, 83% for October-December and 70% for November-January.

El Niño 2026 vs 1997 vs 2015: comparison table

The table compares the three events using NOAA's published indices. The 2026 figures are estimates that NOAA says may still be revised.

Data as of 23 October 2026. Sources: NOAA CPC ONI (ERSST v6) and RONI tables; NOAA CPC ENSO diagnostic discussion of 8 October 2026; NASA Earth Observatory.

Two points stand out. On the traditional ONI, the July-September 2026 reading of +2.2°C is already higher than either 1997 or 2015 at the same stage. On RONI, which strips out some of the global warming background, 2026 sits between the two earlier events. If CPC's forecast holds, 2026-27 would pass the RONI peaks of both 1997-98 and 2015-16.

What strong El Niño years meant for rainfall and temperature

The patterns below come from the observed record, mainly NOAA's own assessment of the 1997-98 event and WMO's summary of typical El Niño impacts. They describe what has happened before, not what will happen this winter.

Established patterns

• Peru and Ecuador: NOAA's assessment of 1997-98 recorded flooding, mudslides and extremely heavy rain in Peru. Warm water reaching the coast, the feature NASA highlights in 2026, is what feeds those coastal storms.
• Southeastern South America: More storms and rainfall in 1997-98, while the Amazon basin saw below-normal rain and forest fires.
• Indonesia and Southeast Asia: In 1997, parts of Sumatra and Borneo had almost no rain from mid-July to early September. Combined with land-clearing burns, NOAA said this fuelled extensive wildfires that it called an ecological disaster. WMO lists drought in Indonesia as a typical El Niño effect.
• Australia: WMO lists drought in eastern and northern Australia among the typical effects.
• Southern Africa and South Asia: WMO links El Niño to drought in southern Africa and to weaker monsoon rainfall in parts of South Asia.
• East Africa: WMO says El Niño often brings a wetter-than-normal October-December "short rains" season. In 1997-98, NOAA noted the rainy season continued into February 1998.
• United States: The 1997-98 winter was wet and stormy across California and the southern states, while much of Canada and the central and northeastern US had record or near-record warmth, according to NOAA.

Global temperature

El Niño releases ocean heat into the atmosphere, so it tends to lift global temperatures, with the biggest effect in the year after it forms. WMO notes that 2024, the hottest year on record, followed the 2023-24 El Niño combined with human-driven warming. WMO also says there is no evidence that climate change makes El Niño more frequent or more intense, though a warmer climate can amplify its impacts.

Forecasts, not certainties

CPC's October discussion stresses that an event of this size makes El Niño-like impacts more likely but does not guarantee them. In the US, the National Weather Service office in Tampa Bay says CPC's 2026-27 winter outlook favours above-normal rain for Florida as the jet stream shifts south. It also notes that very strong El Niño winters there have produced more than double the severe-weather reports of other ENSO phases.

Willis described the uncertainty more bluntly. Outside the tropics, he said, the signal gets muddled, and "there's always a bit of a dice roll here."

What it means

For anyone searching "El Niño 2026", the short answer is that the event is already very strong. The two agencies that track it most closely, NASA from space and NOAA from ocean buoys and models, now describe it in terms usually reserved for 1997-98.

The NASA maps add one specific warning. In 1997, the warm water reached South America and the coastal impacts followed. In 2015 it largely did not. In 2026 it has, which is why Willis expects impacts closer to 1997 than to 2015.

The main uncertainty is how the signal travels beyond the tropics. Regional outcomes will depend on other factors such as the Indian Ocean Dipole and, in North America, the Arctic Oscillation. Governments in historically exposed regions, including Peru, Indonesia, eastern Australia and southern Africa, tend to plan around the established patterns rather than wait for confirmation.

Ocean warmth on this scale also matters for marine life. Bullquill's coverage of the IUCN warning on coral reef collapse explains why long marine heatwaves are a leading threat to reefs. Our explainers on NASA's Thwaites Glacier sea-level projections and the UNEP Emissions Gap 2026 report cover the longer-term warming trend that El Niño sits on top of. More coverage is in our Science section.

NOAA's next ENSO diagnostic discussion is scheduled for 12 November 2026. It will show whether the October-December season is on course for the historic threshold.

Sources

• NASA Earth Observatory: El Niño Then and Now (23 October 2026)
• NOAA Climate Prediction Center: ENSO Diagnostic Discussion (8 October 2026)
• NOAA CPC: Oceanic Niño Index (ERSST v6)
• NOAA CPC: Relative Oceanic Niño Index (RONI)
• NOAA CPC: The strong 1997-98 El Niño and transition to a La Niña episode
• World Meteorological Organization: El Niño/La Niña
• WMO: Global Seasonal Climate Update for September-October-November 2026
• National Weather Service Tampa Bay: Winter Outlook 2026-27 and ENSO's Effect on Our Weather