NOAA (National Oceanic and Atmospheric Administration)’s Climate Prediction Center (CPC) said in an advisory dated September 10, 2026, that this fall and winter’s El Nino has a greater than 90% chance of reaching “very strong” strength. The same advisory raised the odds of something the agency calls a “historic” event to 75%, up from 69% in its prior monthly assessment.
El Nino is a periodic warming of surface waters in the central and eastern Pacific Ocean that shifts weather patterns across much of the world for a season or more. CPC’s advisories track how strong the current one is likely to get and update the odds roughly once a month.
“Historic” has a precise definition in CPC’s own language: a three-month average of at least +2.5 degrees Celsius on an index called RONI, covering October through December 2026. If that threshold is reached, CPC says the event would exceed every El Nino in the record dating back to 1950 by that specific measure. It is a forecast for a window that has not finished yet, not a result already in hand.
Key facts
- September 10, 2026 advisory: CPC put the odds of this El Nino reaching “very strong” strength at greater than 90%.
- “Historic” odds: 75%, up from 69% in CPC’s prior monthly assessment.
- “Historic” threshold: a three-month average of at least +2.5 degrees Celsius on the RONI index for October through December 2026.
- Index switch: CPC moved its official strength measure from ONI to RONI on February 1, 2026.
- Raw Nino-3.4 reading: +1.8 degrees Celsius above average for August 2026 — a different figure from the RONI “historic” threshold.
- 1982-83 comparison: that event’s own peak RONI value is estimated at roughly +2.4 to +2.69 degrees Celsius.
- Seasonal outlook: a separate CPC product released August 20, 2026, covering December 2026 through February 2027.
- Next update: CPC’s next scheduled advisory is October 8, 2026.
Timeline
- February 1, 2026: CPC switched its official El Nino strength index from ONI to RONI.
- August 20, 2026: CPC released its seasonal outlook for December 2026 through February 2027.
- September 10, 2026: CPC’s advisory put the odds of “very strong” strength above 90% and raised the odds of a “historic” event to 75%, up from 69%.
- October 8, 2026: CPC’s next scheduled update on this El Nino.
What the winter is expected to look like
CPC released a separate seasonal outlook on August 20, 2026, three weeks before the September advisory. It covers December 2026 through February 2027 — the coming winter.
Temperatures are favored to run above normal across much of the West, the northern tier of states, and parts of the East, with the strongest odds stretching from the Pacific Northwest to the Midwest. Local Central Texas coverage describes CPC’s guidance as leaning wetter than normal with near-to-below-normal temperatures. Precipitation is favored to run above normal across the southern tier — including Southern California, Arizona, New Mexico, Texas, the Gulf Coast, and the Southeast — and up the East Coast. The Pacific Northwest, the northern Rockies, the northern Plains, and, later in the season, the Great Lakes region are favored to see below-normal precipitation. Because this is characterized as an eastern-Pacific-based El Nino, CPC’s outlook language points to a delayed southern-tier wet signal, with precipitation coverage peaking from January through March 2027 rather than immediately.
For a sense of what an El Nino winter can feel like at street level: Austin-area media report that across past El Nino winters, the city’s average December-through-February temperature ran about 1.3 degrees Fahrenheit colder than in non-El Nino winters, and average rainfall was about 7.82 inches — roughly 38% above non-El Nino winters. That is a historical pattern drawn from past events, not a NOAA forecast number for this specific winter; no CPC figure that precise was available for Austin.
Two of the popular farmers’ almanacs disagree with each other about Texas this winter: the Old Farmer’s Almanac calls for a warmer, drier season, while the Farmers’ Almanac calls for a wetter, stormier one. Neither uses CPC’s scientific outlook methodology. CPC’s own outlook leans wetter than normal for Texas, which lines up more closely with the Farmers’ Almanac’s call than with the Old Farmer’s Almanac’s.
Why there are three different numbers floating around
Readers comparing coverage of this story will run into more than one “the number” for how strong this El Nino is, and they are not interchangeable.
CPC changed how it officially measures El Nino strength on February 1, 2026, switching from a longstanding index called ONI (Oceanic Nino Index) to a newer one called RONI (Relative Oceanic Nino Index). RONI takes the same core measurement — sea-surface temperature in a benchmark patch of the Pacific called the Nino-3.4 region — and subtracts the background warming trend of the whole tropical ocean before comparing it. The idea is to isolate El Nino’s own contribution from decades of general ocean warming.
That means the +2.5 degree “historic” threshold in the September 10 advisory is a RONI figure. It is a different number from the raw Nino-3.4 sea-surface temperature reading CPC also reported for August 2026: +1.8 degrees Celsius above average. Here’s the one to hang onto: the 75% “historic” probability driving this story is a RONI number, not that raw +1.8-degree reading — they measure different things, so don’t swap them if you’re repeating this to someone else.
Does this beat 1982-83?
Some outside forecasters and specialist analysts, not CPC’s own advisory text, have raised comparisons to the 1982-83 El Nino, long regarded as one of the strongest on record. One specialist analysis noted that weekly sea-surface anomalies in the eastern Pacific’s Nino-1+2 region have topped +4.0 degrees Celsius only twice in the observational record: in 1982-83 and now in 2026.
But which event actually holds the record depends on which index is used. Here are the three numbers side by side: this winter’s RONI “historic” threshold is +2.5 degrees Celsius; this winter’s raw Nino-3.4 reading, as of August 2026, is +1.8 degrees Celsius; and 1982-83’s own peak RONI value is estimated at roughly +2.4 to +2.69 degrees Celsius.
- Under the older ONI method: 2015-16 ranks as the strongest El Nino since 1950 (approximately +2.6C), ahead of 1997-98 (approximately +2.4C), with 1982-83 third (approximately +2.1C).
- Under RONI, the metric CPC now uses officially: 1982-83 ranks strongest instead.
Crossing CPC’s +2.5 degree “historic” bar would still put this winter ahead of most El Nino events on record. But it would not automatically make this winter the single strongest event overall, because some estimates put 1982-83’s own peak RONI value at or above that same +2.5 mark. CPC’s September 10 text does not itself name 1982-83 as a comparison point.
The climate-change question
A study led by researcher Julia Cole, built on roughly 1,000 years of coral records from the Galapagos, found that El Nino events are now more than 36% stronger than in the pre-industrial era. The study’s authors attribute that trend to human-caused climate change.
That finding belongs to this one study, not to CPC or NOAA. It is not part of the September 10 advisory, and several other outlets that covered the same advisory did not mention a climate-change link at all. Treat it as one research team’s conclusion about the long-term trend, not as an official government position on this particular winter’s event.
What comes next
CPC’s next scheduled update on this El Nino is October 8, 2026. Separately, NOAA’s flagship, press-briefed Winter Outlook — a different product from the routine monthly ENSO (El Niño/Southern Oscillation) advisories — had not been released as of September 12, 2026; in recent years it has come out around the third Thursday of October.