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The developing El Niño in the Pacific Ocean, which scientists have been monitoring closely for many months, has now exceeded previous records, making it the strongest event in the observational record. 

While forecasts had consistently indicated that 2026 could see an unprecedented El Niño, the latest observations confirm sea-surface temperatures in the central equatorial Pacific have now surpassed levels recorded during any previous event. This milestone represents a significant moment and is likely to have far-reaching impacts on weather patterns around the world. The Met Office will continue to monitor developments closely as the event builds towards its seasonal peak later this year.  

What is El Niño?

El Niño is a naturally-occurring climate phenomenon that develops in the tropical Pacific Ocean. It occurs when sea-surface temperatures across the central and eastern equatorial Pacific become significantly warmer than average. These changes alter atmospheric circulation patterns and can influence weather around the globe. 

Although El Niño originates in the tropical Pacific, its effects are felt far beyond the region. Through interconnected atmospheric processes, it can influence rainfall, temperature and storm tracks across many parts of the world, affecting everything from agriculture and water resources to ecosystems and energy demand.   

A truly unprecedented event 

Professor Adam Scaife, Head of Long Range Prediction at the Met Office, said: “We have been signalling for months that the developing El Niño will be an unprecedented event. The fact that it has already exceeded previous records – with several weeks to go before it peaks later this year – shows the enormity of this El Niño. Scientists are still assessing whether the impacts will be in proportion to its magnitude, but we are already seeing expected effects worldwide.” 

The extraordinary strength of the event highlights the importance of seasonal forecasting and ongoing international monitoring of the climate system as scientists work to understand the implications for the months ahead. 

How is El Niño measured? 

There are multiple ways to measure the strength of an El Niño, and scientists use several complementary metrics to assess its development. 

The most widely used measure is the Oceanic Niño Index (ONI), which is based on sea-surface temperature anomalies in the Niño 3.4 region of the tropical Pacific. The Niño 3.4 region is a large area of the equatorial tropical Pacific Ocean, halfway between South America and Australia. It is the key part of the Pacific that scientists monitor because temperature changes there are closely linked to the development of El Niño and La Niña events. Sustained temperatures above average in this region indicate the presence and strength of El Niño conditions. 

However, recent research has highlighted the value of alternative measures such as the Relative Oceanic Niño Index (RONI). Unlike ONI, which compares Pacific temperatures with a long-term historical average, RONI measures how warm the Niño 3.4 region is relative to the rest of the tropical oceans. This can provide additional insight in a warming climate, where rising background ocean temperatures can mask or amplify different aspects of the El Niño signal. 

Scientists therefore examine a range of indicators, including ONI, RONI, atmospheric pressure patterns, trade wind strength and subsurface ocean temperatures, to build a complete picture of the event and its likely impacts. With different methods used, it is expected that more announcements will follow with further evidence that the event has surpassed previous records as different thresholds are passed.  

Global impacts already emerging 

Historical evidence shows that El Niño can significantly alter global rainfall patterns. Regions that often experience reduced rainfall during El Niño events include parts of Central and northern South America, the western Pacific and areas affected by the Indian summer monsoon. This year's monsoon has already been running below normal, consistent with the developing El Niño signal.  

Other areas, such as southern Africa, may face an increased risk of drought as the event strengthens. El Niño also reduces tropical cyclone activity in the Atlantic through increased wind shear associated with El Niño which tends to suppress hurricane development, and it is notable that we have seen no hurricanes so far this year. 

What could it mean for the UK? 

Although the UK is thousands of miles from the tropical Pacific, El Niño can influence weather patterns across Europe through remote atmospheric connections. 

As the event approaches its winter peak, there is an increased likelihood of wetter and stormier conditions across north-west Europe, including the UK, during autumn and early winter. While El Niño is only one of many factors influencing the UK's weather, its growing influence may therefore increase the chances of a more unsettled period during the coming months.  Later in the season, El Niño is associated with increased risk of cold snaps. 

Seasonal forecasts will continue to incorporate the latest ocean and atmospheric observations to assess how these signals evolve. 

Implications for global temperatures 

Strong El Niño events are typically associated with a rise in global average temperature because additional heat is released from the ocean into the atmosphere which then spreads around the globe, further warming other ocean basins. As a result, exceptionally strong El Niño events can contribute to record-breaking global temperatures in the year following their peak.  

Met Office Science Fellow Dr Nick Dunstone explains: “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. Hence, 2027 is very likely to replace 2024 as the warmest year on record and be yet another year to temporarily exceed +1.5 C above the pre-industrial period”. 

The current event is developing against a backdrop of long-term human-induced climate change, meaning its effects are superimposed on an already warming climate. Understanding how these natural and human influences interact remains a key focus of climate science. 

Continuing to monitor developments 

The Met Office will continue to monitor this unprecedented El Niño as it evolves. While many of the broad-scale impacts associated with El Niño are well understood, the sheer magnitude of the current event means scientists will be paying particularly close attention to how weather and climate patterns respond around the world. 

As further observations become available, forecasts will be updated to provide the latest assessment of the event, its global consequences and any implications for the UK.

About this blog

This is the official blog of the Met Office news team, intended to provide journalists and bloggers with the latest weather, climate science and business news, and information from the Met Office.