El Niño Reaches +2.0°C on NOAA's Official Index, 0.10°C Behind 1997, as WMO Warns of More Extremes in 2027

Since NOAA's Climate Prediction Center said on Oct. 8 that chances remained high for a historic El Niño, the agency's weekly update of Nov. 9 has put a firm number on how close the event is to the record books. The August–October value on NOAA's Relative Oceanic Niño Index (RONI) is +1.97°C, rounded to 2.0°C.

That is the second-highest reading for that time of year since records began in 1950. Only 1997 was higher, at +2.07°C.

The gap to 1997 is shrinking

The 2026 event has trailed 1997–98 for months, but the gap is narrowing. It was 0.14°C behind in June–August, 0.15°C in July–September and 0.10°C in August–October.

It has already passed 2015–16 for this point in the calendar. That event stood at +1.80°C in August–October 2015 and went on to peak at +2.25°C. The all-time three-month high in NOAA's record is +2.40°C, set in December–February 1982–83.

NOAA cautions that the newest RONI values are provisional and can change for up to two months after they are posted. A gap of 0.10°C could move.

What the old peaks imply

The open question is how much more the event gains. From August–October to their peaks, the RONI rose 0.21°C in 1997–98, 0.45°C in 2015–16 and 0.76°C in 1982–83.

Applied to 2026, those gains would produce peaks of about +2.18°C, +2.42°C and +2.73°C. Only the last two would top the existing record. These are comparisons with past events, not forecasts.

CPC's own bar for a "historic" event is higher than the current record. It defines that as a three-month RONI of +2.5°C or more, and it gave that outcome an 83% chance for October–December and 70% for November–January. CPC expects a strong to very strong El Niño through January–March 2027, with El Niño persisting through March–May and ENSO-neutral conditions favored by April–June.

There is one early sign of a plateau. CPC says warm subsurface temperature anomalies in the central and eastern Pacific held steady from August to mid-October and have decreased slightly since. Surface waters remain very warm, with the latest weekly Niño 3.4 reading at +2.3°C.

Two indexes, two answers

The measurement itself is part of the story. The Weather Company reports that Niño 3.4 waters were 2.5°C above average in the last week of October. Based on daily data and the older Oceanic Niño Index, that would already be an all-time record.

NOAA does not use that measure. CPC works from three-month averages and the RONI, which filters out the background ocean warming from climate change. On that basis, James Belanger, vice president of meteorology at The Weather Company, says the agency is smoothing out short-term swings in the ocean and weather. The official ranking still has 1997 ahead.

Climate scientist Zeke Hausfather has said this El Niño is likely the strongest in 1,000 years, based on tree-ring and coral evidence.

Weather already shifting

Meteorologist Eric Webb says the typical U.S. winter impacts of El Niño have settled in one to two months early. The Weather Company points to two major flash flood events in the Desert Southwest, up to 2 feet of rain on parts of the Florida Peninsula, and a major overnight flash flood in the mountains of northern Georgia and southeastern Tennessee.

The Southeast Regional Climate Center reports record wet falls through Nov. 4 in Albuquerque (5.20 inches), Flagstaff (13.15 inches) and West Palm Beach (34.68 inches). Dozens of central U.S. cities, including Chicago, Dallas, Houston and Nashville, have had a record warm fall through early November.

The Weather Company also ties the El Niño to a quiet Atlantic hurricane season: only one hurricane, the fewest since 1925.

A strong El Niño does not guarantee a given outcome locally. BoulderCAST, which analyzed 10 seasonal models and 131 years of Colorado records, says its outlook is encouraging for the Front Range and eastern plains but more complicated for mountain skiers.

WMO raises the stakes at COP31

On Monday, Nov. 9, as COP31 opened in Antalya, Turkey, the World Meteorological Organization released a report covering January 2025 through September 2026. It says the extremes of 2026 will carry into next year.

"We are supercharging our weather and El Niño will be a risk multiplier," WMO Secretary-General Celeste Saulo said. "Heatwaves, tropical cyclones, and rainstorms are intensifying faster than our historical baselines prepared us for."

UN Secretary-General António Guterres called it "a new age of climate extremes," saying "a supersized El Niño is colliding with a planet already superheated by manmade climate change."

The report cites Europe's summer heat waves, which have been estimated to have killed more than 50,000 people, though scientists say even that is likely an undercount. It also cites the rock-ice avalanche on the Nepal-China border that killed more than 1,300 people, which scientists say was influenced by climate change. Some scientists predict 2027 could be the hottest year on record.

Delegates have about two weeks to negotiate how to move away from fossil fuels and who pays for countries already facing severe impacts.

What comes next

CPC's remaining forecasts for October–December and November–January will settle whether this event clears the +2.40°C record. They will also show whether it reaches the agency's own +2.5°C threshold. The slight subsurface cooling is the open variable: if the gain from here looks like 1997's, the record holds. If it looks like 2015's or 1982's, it falls.