El Nino has returned, and it may become the strongest on record.
The US Climate Prediction Center announced in June that this periodic climate phenomenon is back.
El Nino takes shape when waters in the equatorial Pacific warm and the atmosphere responds.
As it grows, it reshapes weather patterns worldwide: some regions face worsening heat and drought, while others see heavier rain and more frequent floods.
Crops and energy markets are affected, potentially lifting inflation and weighing on economic growth.
This El Nino is overlapping with multiple disasters: India's monsoon has been at its weakest in more than a decade, wildfires in Indonesia have intensified, and Brazil's sugar and coffee output is under threat.
Sea surface temperatures in a Pacific region monitored by Japan's weather agency were 4 degrees Celsius above normal in September, the largest anomaly in nearly 80 years.
US weather agencies forecast an 83% chance that this El Nino will become the most severe since records began in 1950 by the end of 2026.
That forecast has led many to believe it will turn into a super El Nino.
What exactly is El Nino?
El Nino was first noticed by Peruvian fishermen in the 17th century.
They observed that in some years the Pacific was unusually warm around Christmas and named the phenomenon "the Christ child" (El Nino de Navidad).
Normally, trade winds blow from east to west, pushing warm Pacific water toward Asia.
During El Nino, these winds weaken or even reverse.
What triggers this shift is still debated, but it causes warm water to drift toward the Americas, warming large areas of the central and eastern Pacific.
The extra ocean heat alters the atmosphere above, shifting storm tracks and changing rainfall patterns.
How often does El Nino occur?
El Nino has no fixed cycle; it typically appears every two to seven years, with varying strength and duration.
The last event occurred in 2023-2024.
El Nino is part of a larger Pacific climate cycle called the El Nino-Southern Oscillation (ENSO).
This cycle alternates between El Nino, its opposite cold phase La Nina, and neutral conditions in between.
During La Nina, east-west trade winds strengthen, warm water pools further west, and sea temperatures in the eastern Pacific run below normal.
The Pacific is huge, covering about one-third of Earth's surface, which gives ENSO enormous influence over global weather.
Similar patterns exist in the Atlantic and Indian Oceans, but their reach is far smaller.
El Nino and La Nina usually peak from December to January, with effects lasting for months afterward.
What counts as a super El Nino?
El Nino is mainly tracked through sea temperatures in the Nino 3.4 region of the Pacific.
The US National Oceanic and Atmospheric Administration (NOAA) defines El Nino as sea surface temperatures at least 0.5 degrees Celsius above the long-term average over five consecutive overlapping three-month periods; a strong El Nino requires an anomaly of at least 1.5 degrees Celsius; an extremely strong El Nino needs at least 2 degrees Celsius.
In September, sea temperatures in the Nino 3.4 region were 2.1 degrees Celsius above normal.
"Super El Nino" is not an official term used by NOAA, the World Meteorological Organization or other official forecasting bodies.
It has simply spread widely this year as the odds of an extremely strong El Nino have risen.
Extremely strong El Ninos are very rare, with only a handful since 1950, the last in 2015-2016.
The stronger the El Nino, the higher the chance of extreme weather, though disasters are not guaranteed.
How does El Nino change global weather?
El Nino slowly releases heat stored in the Pacific into the atmosphere, often pushing global temperatures to new highs.
NOAA data show the global average temperature in 2024 was 1.5 degrees Celsius above pre-industrial levels.
Scientists expect 2027 may set a new record, replacing 2024 as one of the hottest years in history.
El Nino's effects are uneven, appearing first in the tropics and then spreading to Australia, Asia, the Americas and Africa.
Australia, Southeast Asia, northern US and Canada: typically warmer and drier, with rising drought and wildfire risk; India's monsoon rainfall tends to be disrupted.
Southern US, Chile, Argentina and parts of East Africa: more rainfall and higher flood risk.
In El Nino years, the Atlantic hurricane season often becomes less active.
Stronger wind shear (sudden changes in wind speed or direction) disrupts developing storms.
Hurricanes that do form can still be destructive, but fewer overall storms reduce the toll on coastal communities, infrastructure and oil and gas assets in the Gulf of Mexico.
From June to November, the Atlantic averages about 14 named storms a year (winds of 63 kilometers per hour earn a name).
Because of El Nino, NOAA forecast only 7 to 13 this year.
By early October, only one storm had strengthened into a hurricane.
By contrast, Pacific typhoon activity tends to increase in El Nino years.
Warmer seas give tropical storms more energy, raising typhoon disaster risk in Asia, Hawaii and Mexico.
This season those regions have already been hit by deadly storms with heavy economic losses.
Why do El Nino signals matter?
El Nino is one of the most closely watched climate signals, offering months of advance warning on storms, drought risk, crop output and energy demand.
Power companies rely on ENSO forecasts to gauge heating and cooling loads.
Higher temperatures boost air-conditioning demand, straining grids and even causing blackouts; lower rainfall cuts hydropower output.
Commodity traders watch El Nino's impact on crops, mining, oil and gas production and shipping routes.
Drought can lower water levels in the Panama Canal, which links the Atlantic and Pacific, slowing the flow of goods through one of the world's busiest shipping lanes.
El Nino brings both benefits and costs, but historically the global economic losses tend to outweigh localized gains.
Scientists at Dartmouth College studied the knock-on effects of El Nino events over the following five years and estimated the 1997-1998 super El Nino caused $5.7 trillion in global GDP losses.
How does El Nino affect food production?
Some crops benefit from El Nino.
For example, more rain in California helps avocado and almond output.
But many staple and cash crops, including rice, wheat, palm oil, coffee and sugar, are likely to face heat and drought in their growing regions.
Beyond land agriculture, El Nino also disrupts marine fisheries.
Warm Pacific water moving east suppresses the upwelling of nutrient-rich cold water, reducing plankton and leaving fish short of food.
Some species, such as anchoveta off Peru, move to deeper, colder waters, making them harder to catch; tropical fish swim toward areas that were previously too cold.
Lower crop yields, smaller catches and livestock deaths from extreme weather all threaten global food security and push food prices higher.
Will climate change alter El Nino?
Scientists are still debating how global warming will affect the frequency and strength of El Nino.
Early models predicted these natural phenomena would become more frequent as the planet warms.
But for much of the 21st century, La Nina has dominated instead, showing how much remains unknown about the ENSO cycle.
As the oceans keep warming, some worry El Nino may be overestimated and La Nina underestimated, because strength classifications rely on temperature anomalies relative to past decades.
There is a growing consensus that global warming will amplify El Nino's many effects.
Higher temperatures will worsen drought in dry regions; warmer air can hold more moisture, making downpours more intense when storms occur.
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