The Warm Child
Niño 3.4 +3.3°C NOAA · week of 14 Oct

An interactive field guide · Updated 22 October 2026

The warm child that rearranges the world's weather

Every two to seven years, the surface of the eastern tropical Pacific warms by a degree or more. The winds change, the rain moves, and the effects reach farmers in Malawi, fishers in Peru and firefighters in Borneo. This autumn, the Pacific is in the grip of one of the strongest El Niños ever measured.

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Sea surface temperature, modelled for an El Niño like October 2026's. Move your cursor over the ocean to read it.

00Right now · October 2026

El Niño AdvisoryNOAA alert status · discussion of 8 October 2026 · next update 12 November

The child is back, and it is big.

In June 2026, after two weak La Niña winters, NOAA declared El Niño conditions in the tropical Pacific. The warming ran faster than almost any forecast. By mid-September the event was very strong. On 8 October the US Climate Prediction Center put the chance that it becomes the strongest El Niño since reliable records began in 1950 at more than 83 percent for October to December.

The effects have already arrived. Fires and haze in Indonesia. A dry Panama Canal. Peru's anchovy fishery shut for the rest of the year. Global sea surface temperatures at record highs.

+3.3°C Niño 3.4 sea surface anomaly, weekly NOAA CPC · week of 14 Oct 2026
+5.2°C Off Peru and Ecuador (Niño 1+2), weekly NOAA CPC · week of 14 Oct 2026
>83% Chance of a record-strength event by Oct–Dec NOAA CPC outlook, RONI ≥ 2.5°C
1.63°C Global air temperature above pre-industrial, September 2026 Copernicus C3S
432 ppm Carbon dioxide at Mauna Loa, May 2026, the highest monthly average on record NOAA GML / Scripps
Closed Peru's second anchovy season, a fishery behind about a fifth of the world's fishmeal PRODUCE, October 2026

To see why a patch of warm water matters this much, start where the name comes from: the coast of northern Peru, around Christmas.

01A name from the sea

Fishermen noticed first.

  1. c. 600 CE

    Floods in the desert

    Sediment layers on the north coast of Peru record torrential rains in a land that rarely sees any. Archaeologists link a run of such floods and droughts to the decline of the Moche, who built irrigated cities there.

  2. 1800s

    El Niño de Navidad

    Sailors and fishermen of Paita, in northern Peru, call the warm current that arrives each year around Christmas la corriente del Niño, after the Christ child. In some years it comes stronger, the fish vanish, and rain falls on the desert.

  3. 1876–78

    The Great Drought

    A powerful El Niño coincides with monsoon failure in India, drought in northern China and the sertão of Brazil. Famine kills tens of millions of people across three continents, one of the deadliest climate disasters in recorded history.

  4. 1892

    Into the record

    Captain Camilo Carrillo tells the Geographical Society of Lima about the countercurrent that Paita's sailors know as El Niño. The local name enters science.

  5. 1924

    Walker's seesaw

    Gilbert Walker, sent to India to predict the monsoon after the famines, finds that air pressure over the Pacific and Indian Oceans rises and falls like a seesaw. He calls it the Southern Oscillation. Few take it seriously.

  6. 1969

    One system

    Jacob Bjerknes connects the two. The warm water off Peru and Walker's pressure seesaw are the ocean and the air of a single coupled system. It will be named ENSO: El Niño–Southern Oscillation.

  7. 1982–83

    Caught off guard

    The biggest El Niño of the century arrives with no forecast. Scientists only recognise it months in. Governments fund TOGA, a ten-year research programme.

  8. 1994

    A net of buoys

    The TAO array is completed: about 70 moorings strung across the equatorial Pacific, reporting ocean and wind conditions in near real time.

  9. 1997–98

    The first forecast

    For the first time, an El Niño is predicted months ahead. It still turns into one of the most destructive on record, with about 23,000 deaths worldwide.

  10. 2015–16

    The heat record

    One of the three strongest events since 1950. 2016 becomes the warmest year measured to that point. A third of the Great Barrier Reef's shallow corals die.

  11. 2023–24

    Past 1.5°C

    A moderate El Niño on a hotter planet helps push 2024 to about 1.55°C above pre-industrial, the first calendar year beyond the Paris Agreement's aspirational limit.

  12. 2026

    The child returns

    NOAA adopts a new index that accounts for warming tropics. In June it declares El Niño. By September the event is very strong, and still growing.

02The Pacific at rest

A slice through the widest ocean

Picture the Pacific cut open along the equator, from Indonesia to Peru: about 17,000 kilometres of water. Above the cut is the sky. Below it is the top 300 metres of ocean, where El Niño lives.

The trade winds

Near the equator, steady winds blow from east to west. Sailors called them the trade winds. They drag the sun-warmed surface water toward Asia.

A pile of warm water

The water piles up in the west. The sea near Indonesia stands about half a metre higher than the sea near Ecuador, and it is the warmest large body of ocean on Earth, often above 29°C. Scientists call it the Warm Pool.

The thermocline

Beneath the warm layer lies cold, dense water. The boundary between them is the thermocline. In the west it sits about 150 metres down. In the east the winds have pulled it up to around 50 metres.

Upwelling

Off Peru, cold water rises from below to replace the surface water the winds blow away. It carries nutrients into the sunlight. Plankton bloom, and the anchoveta that eat them support one of the largest single-species fisheries on the planet.

The Walker circulation

Warm water heats the air above it. Over the Warm Pool, moist air rises into towering storm clouds, and Indonesia gets some of the heaviest rain on Earth. High up, the air flows east, sinks over the cool eastern Pacific and returns along the surface as the trade winds. The loop keeps itself going.

03The turn

When the wind falters

Every few years the loop slips. A run of strong westerly gusts in the western Pacific, a westerly wind burst, pushes back against the trades.

A wave you can't see

The burst shoves warm water east as a Kelvin wave. At the surface it is only a few centimetres high. Underneath, it pushes the thermocline down by tens of metres. It crosses the Pacific in about two months.

The east warms

When the wave reaches South America, upwelling draws on warm water instead of cold. The eastern Pacific warms by 2°C, 3°C, sometimes more. The fish dive deep or scatter. This is El Niño.

The feedback

A warmer east means a smaller temperature difference across the Pacific. A smaller difference means weaker trade winds. Weaker trades let more warm water slide east. Bjerknes described this loop in 1969. It is why a small nudge can grow into an event that spans a third of the planet's circumference.

The rain moves

Storms follow the warm water. The rising branch of the Walker circulation shifts to the central Pacific. Indonesia and Australia dry out and burn. The deserts of coastal Peru flood.

And her sister

La Niña is the reverse. The trades blow harder, the cold tongue stretches farther west, and the Warm Pool and its rain crowd into the far west. El Niño, La Niña and the neutral state between them make up ENSO, the El Niño–Southern Oscillation.

04Why it ends

The ocean runs out of heat

An El Niño spends the heat that built it. Warm water spills out of the equatorial band toward the poles, and the ocean hands its heat to the atmosphere. Meanwhile, signals reflected off the western edge of the ocean, called Rossby waves, travel back east and lift the thermocline behind the event.

Within about a year the system resets, and it often overshoots into La Niña. Then the strengthened trades slowly rebuild the pile of warm water in the west, and the cycle can begin again. Physicists call this the recharge oscillator.

Recharged Heat piles up in the west.
The cycle as a loop. Across: Niño 3.4 temperature. Up: warm water stored in the equatorial Pacific. The heat store leads the surface warming by several months, which is why forecasters watch it. After Jin (1997).

05Your Pacific

Run the ocean yourself

Drag the dial to set the Niño 3.4 anomaly, pick a famous year, or send a westerly wind burst and watch an El Niño build from one gust.

0.0°C Neutral
West Pacific
29.6°C
East Pacific
24.0°C
Thermocline, east
45 m
Trade winds
100%

What the world tends to see

    06Taking the pulse

    How do you take the temperature of an ocean?

    Sea surface temperature anomaly, modelled for October 2026. −3°+3°C

    El Niño is defined by one number. Scientists average the sea surface temperature over a box of ocean called Niño 3.4, from 5°N to 5°S and 170°W to 120°W, and compare it with normal. When the three-month average stays at least 0.5°C above normal for five overlapping seasons, it counts as an El Niño. Above 1.5°C is strong. Above 2.0°C is very strong.

    The readings come from moored buoys of the TAO/TRITON array, from about 4,000 Argo floats that drift through the world ocean, diving to 2,000 metres and surfacing every ten days to report, and from satellites that measure sea surface height to within a few centimetres.

    07The record

    Seventy-six years of heartbeats

    Every three-month season since 1950, measured in Niño 3.4. Warm peaks are El Niños, cold troughs La Niñas. Switch the index to see how much the yardstick matters on a warming planet.

    Hover or tap the chart
    Oceanic Niño Index and Relative Oceanic Niño Index, running three-month means, December–February 1950 to July–September 2026. Source: NOAA Climate Prediction Center. On RONI, 1982–83 is the strongest event on record and 2023–24 shrinks from strong to moderate.

    08Teleconnections

    Ripples across the planet

    When the Pacific's rain moves, it bends the jet streams and pressure patterns that steer weather thousands of kilometres away. Scientists call these long-distance links teleconnections. They are tendencies, not certainties: El Niño loads the dice.

    Drag to turn the globe

      09The ledger

      What a warm patch of ocean costs

      El Niño is weather, but its damage is measured in harvests, lives and lost years of growth. The poorest tropical countries pay the most.

      1. 1876–78 Tens of millions

        of deaths in famines across India, China and Brazil, as El Niño-linked droughts met colonial grain policy. Historians count it among the worst disasters of the 19th century.

      2. 1982–83 77%

        of the Galápagos penguin population was lost as warm water emptied the sea of fish. Eastern Pacific coral reefs lost most of their living coral.

      3. 1997–98 23,000

        deaths, and $35–45 billion in direct damage, from floods in Peru and Kenya, fires in Indonesia, storms in California. About a fifth of the world's reefs bleached in the first global bleaching event.

      4. 1997–98 $5.7 trillion

        in lost global income over the five years that followed, according to a 2023 study in Science. Economies in the tropics were still smaller years later than they would otherwise have been.

      5. 2015 100,000

        estimated premature deaths across Indonesia, Malaysia and Singapore from the smoke of peat fires that burned through an El Niño drought.

      6. 2016 30%

        of the shallow-water corals on the Great Barrier Reef died in a single marine heatwave.

      7. 2023–25 84%

        of the world's coral reefs were hit by bleaching-level heat in the fourth and largest global bleaching event, across 82 countries and territories.

      Global surface temperature °C above 1880–1900

      10The rising floor

      El Niño now plays on a warmer stage

      El Niño is natural. It is not caused by climate change. But it now happens on a planet that people have heated, and the two add together.

      A century and a half of heat

      Each bar is a year of global average temperature. Since the late 1800s the planet has warmed about 1.3°C, driven by the carbon dioxide and methane we add to the air. Carbon dioxide has gone from about 280 parts per million before industry to 432 this May.

      The wobble on top

      Colour the years by the state of the Pacific and a pattern appears. El Niño years run hot, because the ocean releases stored heat into the air. La Niña years run cool. ENSO swings the global average by one or two tenths of a degree.

      A staircase of records

      Nearly every new record lands on an El Niño. 1998. 2010. 2016. 2024. Each event lifts the planet onto a new step, and the trend makes sure it never goes back down to the old floor.

      Today's cool years beat yesterday's hot ones

      2025 began and ended with La Niña, yet it was warmer than 2016, the record year that followed the great 2015–16 El Niño. The cold phase of today is the hot phase of a decade ago.

      And 2026 is not finished

      Global temperatures lag the Pacific by a few months. This El Niño will deliver most of its heat to the atmosphere over the coming winter, which is why 2026 and 2027 could both challenge 2024's record of about 1.55°C above pre-industrial.

      11The months ahead

      What this winter may bring

      El Niño usually peaks between November and February, and its effects run into the following year. Forecasters expect this one to peak around the end of 2026. NOAA's next update is due on 12 November.

      Strength does not decide damage on its own. The warm Atlantic and a likely positive Indian Ocean Dipole will shape what happens in each region. But the odds now tilt strongly toward a familiar list: drought across southern Africa, Indonesia, the Philippines and northern Australia; heavy rain on the coasts of Peru and Ecuador and across the southern United States; a mild winter in Canada and the northern US; coral bleaching through the southern summer.

      Scientists are less sure about the long run. Many climate models project that extreme El Niños become more frequent as the planet warms, roughly doubling under high emissions. Others disagree, and the Pacific's own recent trends do not yet match the models. What is certain is the stage: each El Niño now starts from a higher floor than the last.

      Chance of a record El Niño

      54%Sep–Nov
      83%Oct–Dec
      70%Nov–Jan
      Probability that the three-month RONI reaches +2.5°C or more, beyond any event since 1950. NOAA CPC, 8 October 2026.

      The child leaves.
      The heat stays.

      By spring 2027 this El Niño will fade, as they all do. The ocean will keep the heat we have added to it. More than nine-tenths of the extra energy trapped by greenhouse gases has gone into the sea. The next child will be born into warmer water.

      Run the Pacific again