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How we track El Niño and La Niña

What the dashboard shows, where the numbers come from, and what they can’t tell you.

The short answer

El Niño and La Niña are the warm and cool phases of a cycle in the tropical Pacific, the El Niño–Southern Oscillation (ENSO). Normally the trade winds push warm surface water west, toward Indonesia, and cold water wells up off Peru and Ecuador. In El Niño the winds weaken, warm water spreads east and the tropical rain belt moves with it. In La Niña the winds strengthen and the eastern Pacific cools. Because the ocean and the winds reinforce each other, a change that starts in the Pacific shifts the odds of drought, floods and heat around the world.

The dashboard answers two questions: which phase are we in officially, and is the next change already under way before the official label catches up?

How we know

The official index. Since February 2026, the US National Oceanic and Atmospheric Administration (NOAA) measures ENSO with the Relative Oceanic Niño Index (RONI). It takes how much warmer or cooler than normal the central equatorial Pacific (the “Niño 3.4” region) is, and subtracts how much warmer or cooler the tropical oceans as a whole are, averaged over three months. NOAA switched because the old index, the Oceanic Niño Index (ONI), was increasingly inflated by the warming of the whole tropics: it partly measured climate change rather than the El Niño cycle. Under the new index, El Niños generally come out a little weaker and La Niñas a little stronger.

An El Niño needs the index at +0.5 °C or above, and a La Niña at −0.5 °C or below, for five overlapping three-month periods in a row. +1.5 °C and above is called strong. “Super” El Niño, +2.0 °C and above, is an informal label, not a NOAA category.

Why the raw numbers look higher. The dashboard also shows the plain monthly temperature anomalies for the Niño 3.4 region and for the far eastern Pacific off Peru (Niño 1+2). These are not adjusted for the warming of the whole tropics, so they read higher than the official index. The eastern region often warms first and matters most for Peru’s fisheries and coastal rains.

The atmosphere. The Southern Oscillation Index (SOI) compares air pressure at Tahiti and Darwin. A negative SOI means the winds are behaving like El Niño; positive, like La Niña. When ocean and atmosphere agree, an event is more likely to last.

The super El Niño comparison

The comparison chart lines up the big El Niños of 1972–73, 1982–83, 1997–98 and 2015–16 from the season each one began, and draws the current event on the same scale. It compares shapes: is this event climbing as fast as those did? It is not a forecast. On NOAA’s new index, those events peaked between +1.97 °C (1972–73) and +2.40 °C (1982–83); 1991–92 also passed +2.0 °C.

How current each part is

We check NOAA’s files every night.

What the dashboard can’t tell you

It is not a forecast. ENSO forecasts need climate models, measurements below the ocean surface and expert judgment; NOAA’s monthly outlook, quoted on the page, gives the official odds.

The “near you” section describes the usual El Niño pattern for your region, such as wetter winters in the southern United States or drought risk in Indonesia and Australia. Each event is different, and a warmer climate changes the odds.

And it cannot say that a given coral bleaching, drought or marine heatwave shown on the page was caused by El Niño. Those tiles show systems El Niño often affects; working out the cause needs separate analysis.

Further reading

Credits

NOAA’s Climate Prediction Center publishes every index used here, built on ocean measurements from ships, buoys and satellites. The impact tiles come from the other dashboards on this site. This dashboard collects and presents their work.

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