El Nino expected to develop soon, but its strength remains uncertain

El Nino is expected to develop soon, potentially bringing significant impacts to our weather, the upcoming hurricane season and global temperatures, although "substantial uncertainty” regarding its peak strength remains, according to the latest forecast from the National Oceanic and Atmospheric Administration (NOAA).

NOAA's updated forecast puts the chance of El Nino developing in May through July at 82%, with the climate event expected to last through the upcoming Northern Hemisphere winter. NOAA issued an El Nino Watch on March 12, citing favorable conditions for its development over the next six months.

El Niño refers to the warmer-than-average phase of the El Nino–Southern Oscillation (ENSO), a natural cycle where sea surface temperatures across the central and eastern equatorial Pacific Ocean rise and fall. The cooler-than-average phase is called La Nina, while near-average conditions are known as ENSO-neutral.

Currently, ENSO-neutral conditions remain in place, however, sea surface temperatures have shown a notable warming trend in recent weeks, especially in the central and eastern equatorial Pacific Ocean, reflecting the transition towards El Nino conditions.

NOAA ranks the strength of El Nino events by measuring the sea surface temperature departure from average (anomaly) across this region, classifying events as weak, moderate, strong or very strong. Currently, no strength category exceeds a 37% chance of occurrence through the end of the year.

"There is substantial uncertainty in the ultimate strength of El Nino," Michelle L'Heureux, a physical scientist at NOAA's Climate Prediction Center, told ABC News. "While there is a 2-in-3 chance of a strong or very strong El Nino for the November-January 2026-27 season, there is still a 1-in-3 chance of an event weaker than that."

According to NOAA, the strongest El Nino events in the historical record are characterized by significant ocean-atmosphere coupling, which is how the two interact and influence each other, through the summer, and it remains to be seen whether this occurs in the coming months.

"El Nino depends on the tropical Pacific ocean and atmosphere interacting in a way that reinforces the event," L'Heureux added. "For example, we need to see weaker than average trade winds along the equatorial Pacific Ocean because that will help keep the ocean surface temperatures above average."

NOAA also noted that stronger El Nino events can only make certain impacts more likely and do not always guarantee strong impacts. The World Meteorological Organization (WMO) echoed these concerns in its latest Global Seasonal Climate Outlook, saying "a key source of uncertainty is related to the potential intensity and duration of the El Nino event."

It also acknowledged growing speculation regarding how strong the event could become, adding that "while some model forecasts indicate the possibility of stronger conditions later in the year, there is currently no consensus or sufficient confidence to confirm or exclude a high-intensity event."

While adjectives such as "super" and "extreme" are popular ways of describing the strength of an El Nino event on social media, NOAA and the WMO classify the strength as weak to moderate, strong, and very strong. The WMO noted in a recent statement that "the term [[super]] is not part of standardized operational classifications."

Despite ongoing uncertainty in some aspects, experts say El Nino remains one of the best-understood and most predictable climate patterns.

"Their common features allow us to issue probabilities for impacts on temperature and precipitation," said L'Heureux. "We can often see El Nino forming in advance of impacts so it allows us to prepare and mitigate its influence."

El Nino and La Nina events occur at irregular intervals, typically every 2 to 7 years. El Niño has been somewhat more frequent than La Nina in past observations, but both phases vary in timing and intensity from one cycle to the next.

Typical El Niño impacts across the U.S.

Impacts from El Nino, similar to La Nina, tend to be most consistent and pronounced from late autumn through early spring following the event’s onset, NOAA says. There is usually a delay between the onset of the event and its associated effects.

Typically, during El Nino, the northern half of the United States and parts of Alaska are more likely to see warmer-than-average temperatures, with near- to below-average temperatures favored along the southern tier of the U.S., most likely from Texas to the Southeast.

For precipitation, wetter-than-average conditions are typically observed along the southern tier of the U.S. in parts of California, the Southwest, Gulf Coast and Southeast. Below-average precipitation is frequently observed across parts of the northern Rockies, south-central Mississippi Valley, Ohio Valley and Great Lakes regions.

El Nino typically increases the odds of above-average snowfall in the southern Rockies, south-central Plains, mid-Atlantic and coastal areas of the Northeast, with below-average snowfall favored in the northern Rockies, northern Plains and Great Lakes regions.

Experts caution that the impacts on weather patterns are nuanced. Each season is different, and typical El Nino conditions don’t always materialize.

"Every El Nino is unique in some way," L'Heureux added. "Every El Nino has a distinctive appearance and evolution."

El Niño’s influence on hurricane season activity

The impact of El Nino on this year’s Atlantic and Eastern Pacific hurricane seasons will largely depend on how quickly it develops and how strong it gets. Even so, El Nino is only one of several important variables which influence tropical activity.

El Nino conditions often suppress activity during the Atlantic hurricane season by producing unfavorable atmospheric winds. In the Eastern Pacific, the opposite occurs, with favorable conditions supporting above-average hurricane season activity.

"El Nino increases convection (thunderstorms) across the eastern and central Pacific, which causes downstream wind shear over the Atlantic from strong upper-level winds," said Andy Hazelton, an associate scientist at the University of Miami's Cooperative Institute for Marine and Atmospheric Studies.

Vertical wind shear, which refers to changes in wind speed and direction with height in the atmosphere, is often a primary factor in below-average hurricane season activity. Strong vertical wind shear can tear a developing tropical system apart or even prevent it from forming, NOAA says.

"The rising motion over the Pacific also leads to increased subsidence (sinking air) over the Atlantic, which suppresses thunderstorms and tropical cyclone development," Hazelton added.

Other factors, such as sea surface temperatures, also play an important role in tropical cyclone development and strength. Unseasonably warm ocean waters can partially offset the effects of unfavorable atmospheric winds, according to forecasters.

NOAA is expected to issue its official hurricane season outlook next Thursday, May 21. The Eastern Pacific season begins May 15, followed by the Atlantic season on June 1.

Global temperature records could be challenged again

So far, 2024 ranked as the planet’s warmest year on record, following the last El Nino event, which emerged in mid-2023 and persisted through spring 2024, according to NOAA. However, with El Nino conditions expected to return in the coming months, global temperature records could be challenged again.

While global air and sea surface temperatures are currently falling short of new record highs, climate scientists warn this pause is unlikely to last. Record highs in global average temperature often occur during El Nino years, combined with the long-term global warming trend driven primarily by human-caused greenhouse gas emissions.

"Warmer ocean temperatures associated with El Nino, together with its tendency to favor warmer conditions in many areas, often contribute to warmer than normal global annual temperatures," Jon Gottschalck, Chief of the Operational Prediction Branch at NOAA’s Climate Prediction Center said.

According to NOAA, 2025 ranked as the third-warmest year on record globally, trailing 2024 and 2023. The slightly lower ranking came amid recent La Nina conditions, which typically cause a temporary dip in global average temperatures.

There is usually a delay between the onset of El Nino and its peak impacts on global temperatures, NOAA says. As with the most recent event, its greatest influence often occurs in the months after it peaks, which can keep global temperatures elevated into the following year. The intensity of the developing El Nino will play a major role in whether global temperature records could be challenged in the near future.

According to the latest outlook from NOAA’s National Centers for Environmental Information, the likelihood that 2026 will rank among the five warmest years on record is about 96%, while the probability of it becoming the warmest year is less than 1%. However, those odds could rise significantly in 2027, depending on how the event unfolds.

"The WMO community will be carefully monitoring conditions in the coming months to inform decision-making. The most recent El Nino, in 2023-24, was one of the five strongest on record and it played a role in the record global temperatures we saw in 2024," WMO Secretary-General Celeste Saulo said in a recent statement.