What is a ‘super El Niño’ and when will it impact the UK?

The meteorological phenomenon known as El Niño is set to have wide-ranging impacts on weather in the UK throughout the coming months. The Met Office predicted that this year’s “unprecedented” event, expected to be the strongest “in living memory”, will cause a stormy autumn and winter before the record-breaking heat continues. This will likely come after a forecasted cooler rest of August, with an increase in rain after an extended summer dry spell. September brings the possibility of another heatwave with warnings that temperatures could rise again to as high as 34°C. Shorts What is El Niño – and its ‘super’ version? El Niño is the biggest fluctuation in the world’s climate system, known as the El Niño-Southern Oscillation (ENSO) cycle. Typically occurring once every two to seven years and lasting nine to 12 months, an El Niño event is declared when sea temperatures in the tropical eastern Pacific rise 0.5°C above the long-term average, with varied effects on rainfall patterns and temperatures across the globe. A “super El Niño” is broadly defined as when tropical Pacific sea surface temperatures reach 1.5-2°C – or more – above average. These events are rare; there have been only five since 1950 with the most recent occurring in 2015-16, resulting in 2016 becoming the hottest year on record at that time. The Met Office’s forecasts suggest this year’s warming will exceed 3°C. “El Niño occurs when warm water that’s built up in the West Pacific sloshes to the east and replaces that normally cold water with warmer water,” Paul Roundy, professor of atmospheric sciences at the University of Albany, told Time magazine. With these effects often peaking in December, the name given to the natural event – which means “the boy” in Spanish – is thought to have originated centuries ago as “El Niño de Navidad” when Peruvian fishermen named the weather phenomenon after the newborn Christ. The opposite weather event to El Niño is La Niña – “the girl” – when temperatures fluctuate downward, with average sea surface temperatures in the equatorial Pacific dropping by 3-5°C below average. A La Niña event beginning in December 2024 temporarily gave the planet lower global temperatures and meant that 2025 was cooler than 2024, which was the world’s hottest year on record. A dried up lake near the village of Strensham in Worcestershire (Photo: David Davies/PA Wire) ‘Unprecedented’ El Niño event in 2026 The more than 3°C rise in sea temperatures forecast in the coming months makes this year’s El Niño “the largest since the 19th century.” “I have never seen an El Niño signal this intense in our forecasts,” said Professor Adam Scaife, Head of Long Range Forecasting at the Met Office. He added: “A typical El Niño leads to an equatorial Pacific sea-surface temperature rise of between one to 2°C, with 2°C being a really big event. “This implies that if the forecast is accurate – and other forecast systems show similar extreme values – then 2026 will far exceed our recent experience of El Niño and its worldwide climate influences.” El Niño is associated with widespread changes in the climate system that can last for several months and lead to significant human impacts affecting areas including infrastructure, agriculture, health and energy sectors. How will El Niño impact the UK’s weather? The climate effects of El Niño vary across the world; it can affect hurricane season in the Caribbean, monsoon season in Asia or droughts in South America and Australia, with the strongest effects felt in areas closest to the Pacific. North-western Europe, meanwhile, including the UK, is forecast to see wetter and stormier conditions this autumn and early winter, the Met Office said. El Niño events also drive an increase in global average temperatures, with 2027 now forecast to be the warmest year on record – meaning that after a summer of record-breaking heat, more historically hot weather is expected to be on the way next year. “During large El Niño events, significantly more heat is released from the ocean to the atmosphere leading to an increase in global average temperature, particularly in the calendar year following the winter peak of the El Niño,” said Dr Nick Dunstone, Science Fellow at the Met Office. “Hence, 2027 is very likely to replace 2024 as the warmest year on record and be another year to temporarily exceed plus 1.5°C above the pre-industrial period”. Studies are ongoing regarding the impact of global warming on El Niño, but the Climate Prediction Centre says that “this amplified cycle translates into more extreme and frequent ENSO-linked droughts, floods, heat waves, wildfires and severe storms.” Could it end UK’s drought conditions? An unprecedented string of heatwaves and lack of rainfall in recent months brought the driest July in 190 years and pushed almost three-quarters of England and all of Wales into drought, placing severe pressure on the water system, wildlife, farmers, emergency services and infrastructure. Many areas of the country are facing water shortages as reservoir levels have fallen to 62.6 per cent – 16.3 per cent lower than is expected for this time of year, according to the Department for Environment, Food & Rural Affairs. Sudden heavy rainfall this week also sparked fears of flash flooding due to water hitting parched, dry, hard ground. But it is not expected to end the drought: Forecasters and officials warned it could take months of sustained rainfall before rivers, reservoirs and groundwaters are completely replenished, which would mark the official end of a drought. It also warned drought conditions could persist into the new year as, despite El Niño, current forecasts do not suggest this autumn will have the amount of rainfall required to drive recovery before December.