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El Niño has officially begun, and it’s more likely than not that it will develop into a “super” El Niño. Either way, it will amplify temperatures and extreme weather around the world.

El Niño is a natural climate phase that occurs when east-to-west winds weaken in the tropical Pacific, allowing water concentrated in the “warm pool” on the western side of the Pacific to wash back towards the eastern side. This broad smear of warm water heats the atmosphere, raising the global temperature.

The US National Oceanic and Atmospheric Administration (NOAA) has now declared the onset of El Niño because sea surface temperatures in the central-eastern Pacific have been more than 0.5°C above normal for the past month, and climate models project they will remain there for at least the next six months. The Japan Meteorological Agency has also declared that El Niño has begun.

“We are seeing westerly wind anomalies from the dateline almost all the way to about 130° west, so basically the entire area south of Hawaii,” says at NOAA’s National Weather Service. “What that means is significantly reduced trade winds there, so it’s allowing the atmosphere and the ocean to slosh to the east and bring that warm water with it.”

NOAA also said there is a 63 per cent chance this El Niño will become a very strong or “super” El Niño, when sea surface temperatures in the equatorial Pacific breach 2°C above average. It could be the hottest El Niño ever seen.

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“This latest El Niño is likely to be a significant event, perhaps one of the most intense on record,” said at the Met Office, the UK’s weather service, in a statement.

Out of 200 model simulations, none show sea surface temperatures in the central-eastern Pacific going back below 1°C above normal this year once El Niño gets going, according Rosencrans. Several models project sea surface temperatures could reach 2.6°C higher than usual, and one Canadian model says they could even hit 3°C, which would smash the 2.5°C record set during the super El Niño of 1982-83. During that event, flooding killed an 1300 to 2000 people in Peru.

Temperatures will likely peak by the end of the year and simmer well into 2027. This rush of heat comes on top of global warming of 1.36°C, leading scientists to predict that next year will be the hottest ever observed. The boost in temperatures will worsen extreme weather, since a warmer atmosphere holds more energy and moisture. El Niño also tends to bring abnormally wet or dry weather to different regions.

“What it does is change the odds of those rainfalls��or heatwaves or cold snaps happening in certain places,” says Rosencrans. “The atmosphere [is] throwing loaded dice in a way, so you’re more likely to get rainfall in southern California, you’re more likely to get drying in the maritime continent, and potentially even into India [and] the northern parts of Australia.”

The southern US is more likely to see reduced rainfall this summer, followed by cool, wet, stormy weather this winter, with cold snaps possible as far south as Mexico. South-East Asia and south-east Africa could face heat and drought this summer and winter, raising the risk of wildfires.

El Niño can tend to bring colder winters to the UK, but it can also bring warmer, wetter conditions, said independent climate scientist at a briefing. Many other climate factors affect Europe, meaning El Niño impacts are less certain. “It tends to change the storm tracks, and you often get these warmer, wetter conditions,” says Gilbert. “In the past, for the UK, you’ve seen more storm incidents than otherwise… but the direct connection in the UK is less obvious than in the US or Australia.”

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Heat or drought could impact commodities like rice, coffee and chocolate, and disrupt food supplies around the world. If rice yields decline, India – a major producer – could limit exports and cause rice to become scarcer and more expensive in other countries, says at the University of Maryland.

“The impacts… ripple through the food system,” he says. “We think about a commodity like rice, which is important for food security for many people, and we do have concerns about potential monsoon deficits leading to lower rice production.”

El Niño may be getting more frequent, and global warming will regardless exacerbate its consequences, which could compound issues like migration, says at the University of Oxford. “We need long-term preparedness and planning as we continue with climate change and we also continue with El Niño amplifying that.”