El Niño forecast to strengthen toward December peak, WMO says
The UN weather agency expects the Pacific warming event to persist through February 2027, with a potentially record ocean-temperature anomaly and uneven rainfall risks worldwide.
El Niño is expected to strengthen in the central and eastern equatorial Pacific before peaking in December, the World Meteorological Organization said on 8 October, according to RTÉ. The UN weather agency forecasts above-average temperatures across much of the globe and shifting rainfall patterns, increasing drought and flood risks in different regions.
The forecast puts the event on course to become potentially one of the strongest since at least 1950. Its projected ocean-temperature record remains a forecast, however, and the likelihood of a prolonged El Niño does not mean every region will experience a particular weather outcome.
What WMO forecasts through February 2027
“El Niño is firmly established and strengthening rapidly,” WMO chief Celeste Saulo said, as quoted by RTÉ. She put the likelihood that it would persist through February 2027 at nearly 100%. That probability concerns the event’s continuation, rather than the certainty of floods, drought or losses in any individual community.
The monthly Global Seasonal Climate Update described by RTÉ draws on a consensus across 13 leading national and international meteorological centres. It forecasts further strengthening before December’s expected peak, with consequences for economies, ecosystems and communities worldwide. The report does not quantify the potential losses for individual countries.
Pacific temperature anomaly could exceed previous record
The sea-surface temperature anomaly index for the central-eastern equatorial Pacific rose from 1.6°C above normal in June to 2.5°C in August, RTÉ reports. For the October–November–December period, the forecast puts the anomaly at approximately 3.7°C above normal.
According to RTÉ, that would exceed the previous record of 2.6°C set in 2015–2016. The comparison concerns surface waters in a specific Pacific region: it is not a prediction that the global average temperature will rise by 3.7°C. The projected record has yet to be realised.
RTÉ’s account does not specify the reference period used to define normal temperatures for that index, its precise methodology or an uncertainty interval around the projection. The reported figure therefore describes the forecast’s scale without establishing a precise range of possible outcomes.
How El Niño spreads heat beyond the Pacific
El Niño is a naturally occurring warming of surface waters in the central and eastern equatorial Pacific, accompanied by changes in winds, pressure and rainfall. RTÉ describes it as typically recurring every two to seven years and lasting around nine to 12 months, with La Niña and neutral conditions forming the other phases.
Saulo explained that El Niño releases heat already stored in the ocean rather than adding new heat to the planet. “The ocean it’s drawing from is the warmest we’ve ever measured it. There is simply more heat available to release,” she said, according to RTÉ.
In a 2014 NOAA Climate.gov explanation, Anthony Barnston describes how warmer Pacific waters increase thunderstorms. As water vapour condenses, it releases heat higher in the atmosphere, changing circulation far beyond the ocean. These distant connections help explain why a tropical Pacific event affects rainfall elsewhere.
Regional rainfall risks remain uncertain
Barnston identifies recurring rainfall deficits in Indonesia and northern South America, and wetter conditions in southeastern South America, eastern equatorial Africa and the southern United States. The patterns depend on season. An extended winter Pacific jet stream can also bring more storms across the southern US.
His explanation stresses that stronger events make these distant effects more likely, without guaranteeing their occurrence or severity. It supplies historical context, not a local forecast for 2026. A separate example concerns fisheries: warmer waters can drive anchovies off northwestern Peru toward cooler waters, reducing catches. This does not establish current losses.
December peak does not fix the timing of global heat
WMO warns that the natural event compounds human-caused climate change, RTÉ reports. The previous El Niño contributed to the warmth of 2023 and 2024; the latter reached around 1.55°C above the 1850–1900 average. Those historical annual temperatures are distinct from the regional ocean anomaly now being forecast.
El Niño usually peaks between November and February, while the associated temperature spike typically follows later, according to RTÉ. December’s forecast peak therefore does not establish when global temperatures will reach their maximum. The current outlook describes a strengthening ocean event and broad risks, while its eventual regional consequences remain uncertain.
Sources and context
- El Niño to intensify before December peak - UNRTÉ
- How ENSO leads to a cascade of global impactsNOAA Climate.gov; author Anthony Barnston
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