El Niño Could Be Strongest Since 19th Century, Met Office Says

EXETER, UNITED KINGDOM — Met Office forecasts show Pacific warming above 3°C in a key El Niño region, raising the prospect of major weather disruption and record global heat in 2027.

The El Niño strengthening across the tropical Pacific could become the largest event in living memory and probably the strongest since the 19th century, according to a new assessment from Britain's Met Office.

The agency's latest long-range forecast shows sea-surface temperature anomalies exceeding 3°C in the Niño 3.4 region of the equatorial Pacific during the coming months. That would place the event well beyond the range normally associated with a major El Niño and above values seen in the strongest episodes of recent decades.

Professor Adam Scaife, the Met Office's head of long-range forecasting, described the model signal as unprecedented in his experience. Typical El Niño events raise equatorial Pacific sea-surface temperatures by roughly 1°C to 2°C, while an anomaly around 2°C already represents a particularly strong event, the agency said.

The forecast is not a measurement of the eventual peak. El Niño has already developed, but its final intensity remains uncertain and seasonal model projections can change as ocean and atmospheric conditions evolve.

NOAA's Climate Prediction Center said in July that there was an 81% probability of a very strong El Niño during October through December and a 97% probability that El Niño conditions would persist into early spring 2027.

Forecasts now exceed the strongest modern events

The scale of the latest projections marks a significant shift from forecasts issued earlier this year.

In April, the Met Office said the developing event could rank among the strongest of the 21st century and might be comparable with the powerful 1997–98 episode. By June, after NOAA formally declared El Niño conditions, the agency said anomalies were likely to exceed 2°C and acknowledged that some models were projecting record strength.

Its August outlook is considerably more extreme.

The Met Office's GloSea system now projects Niño 3.4 temperatures more than 3°C above normal in coming months. The agency says other forecasting systems are producing similarly exceptional values.

Independent model comparisons point in the same direction. Carbon Brief reported in July that 91% of 667 runs from 14 seasonal forecasting systems projected a peak stronger than the previous historical record. Its analysis found the developing event had already reached the threshold for a strong El Niño by June.

A separate assessment reported by Nature said researchers regarded the event as potentially the largest in at least 150 years.

Those projections do not guarantee that any one model's peak value will occur. Forecast uncertainty tends to narrow as an event approaches its boreal-winter maximum, and the precise atmospheric response matters alongside ocean temperatures.

Why a warmer Pacific changes weather worldwide

El Niño is the warm phase of the El Niño–Southern Oscillation, or ENSO, a naturally occurring interaction between the tropical Pacific Ocean and atmosphere.

It is usually identified through sustained unusually warm water across the central and eastern equatorial Pacific. The Niño 3.4 region — roughly between 5 degrees north and south of the equator and 120 to 170 degrees west — is one of the principal areas scientists monitor.

The warmer ocean alters tropical rainfall and atmospheric circulation. Those changes can then shift jet streams, rainfall patterns and storm behavior across regions thousands of kilometers away.

The effects are not identical during every El Niño.

The Met Office says the current event is already associated with a weaker-than-normal Indian summer monsoon, while Central America, tropical South America and parts of the western Pacific are among regions at elevated risk of below-normal rainfall.

El Niño can also increase vertical wind shear across the tropical Atlantic, generally suppressing hurricane activity there. The Met Office's July seasonal update forecast 12 named Atlantic storms and five hurricanes during 2026, both below the long-term average.

Elsewhere, the pattern can increase rainfall and flood risk. The important qualification is that El Niño changes probabilities rather than dictating individual weather events, meaning a strong global signal does not guarantee a particular outcome in every country.

UK faces a less predictable signal

For Britain and northwestern Europe, the link is more complicated.

The UK lies far from the tropical Pacific, and the atmospheric pathways connecting El Niño to European weather are less consistent than those affecting many tropical and subtropical regions.

A House of Commons Library briefing published in June said previous El Niño episodes have sometimes produced wetter or stormier conditions in the UK, but emphasized that European effects can be difficult to predict and may emerge with a delay.

Recent Met Office analysis points toward an increased likelihood of wetter conditions in northwestern Europe during parts of the event, while the broader atmospheric disruption could affect storm tracks into 2027.

That does not amount to a deterministic forecast of a stormy British winter.

Local weather will continue to depend on the North Atlantic circulation, jet-stream position and other climate patterns, and seasonal forecasts describe shifts in probability rather than exact sequences of storms or rainfall totals.

The distinction is particularly important after an exceptionally dry and hot summer in parts of Britain. The Met Office said July 2026 was the UK's third-driest July on record and the sunniest July in the national series, with especially severe rainfall deficits across parts of England and Wales.

El Niño could alter the odds of wetter conditions later in the year, but it cannot by itself determine whether current drought pressures will end.

2027 could become the hottest year on record

The clearest global consequence may be temperature.

Large El Niño events transfer additional heat from the tropical Pacific Ocean into the atmosphere, tending to lift global average temperatures most strongly in the calendar year after the event peaks.

The Met Office now says 2027 is very likely to replace 2024 as the warmest year in the instrumental record.

That warming pulse would occur on top of the much larger long-term increase caused by greenhouse-gas emissions.

This distinction is fundamental: El Niño is a natural oscillation and does not cause the underlying multidecadal trend in global warming. Human-caused climate change, meanwhile, has raised the temperature baseline from which each El Niño begins.

As a result, a powerful El Niño today can produce global temperatures far above those reached during equally strong events several decades ago.

The Met Office's broader 2026–2030 climate outlook already assigned an 86% probability that at least one year in that period would exceed 2024 as the warmest on record and a 91% probability that at least one year would temporarily exceed 1.5°C above the 1850–1900 average.

A single year above 1.5°C does not mean the Paris Agreement's long-term warming threshold has permanently been crossed. That target refers to sustained climate change assessed over a longer period rather than one unusually hot El Niño-influenced year.

Agriculture and food systems face uneven risks

The potential consequences extend beyond temperature records.

El Niño can alter rainfall during critical planting and growing seasons, creating risks for food production in areas already exposed to drought, water shortages or flooding.

University of Reading climate researchers said the latest forecasts point toward an exceptional event peaking around November or December, with atmospheric effects likely to persist well into 2027. They identified dry conditions already affecting parts of East Africa, Central America and Southeast Asia as areas requiring close attention.

Agricultural consequences will vary by crop and region. Reduced rainfall can damage harvests in one country while increased rainfall benefits production elsewhere or creates flood losses.

Supply-chain effects can also reach countries far from the Pacific through food and commodity prices.

The House of Commons Library has identified agriculture, energy, trade, water resources, supply chains and livelihoods among the sectors potentially affected by a major El Niño.

Peak strength remains the central uncertainty

The strongest claim in the current outlook — that this could be the largest El Niño since the 19th century — is still a forecast rather than an observed final ranking.

Sea-surface temperatures will need to continue developing through the northern autumn before scientists can establish where the 2026 event ultimately sits in the historical record.

Atmospheric coupling will also matter. ENSO is not defined by ocean temperature alone; its strength and impacts depend on the interaction between Pacific warming, winds, pressure and rainfall.

The Met Office says it will continue rerunning its forecasts and working with government departments to assess potential consequences as the event evolves.

The next several months will therefore determine whether the extraordinary model projections become an equally extraordinary observed El Niño — and how much additional heat and weather disruption the event carries into 2027.