El Niño 2026-27 explained: how strong it is and what it means for winter

The El Niño now building in the tropical Pacific is strong and still getting stronger. NOAA's Climate Prediction Center says a strong-to-very-strong event is likely to last through early 2027, and odds favor it becoming the most powerful since record-keeping began in 1950. For Boston and the Northeast, NOAA's winter outlook leans toward a milder and wetter season than usual, though snowfall itself cannot be forecast months ahead.

How strong is El Niño right now?

The Climate Prediction Center (CPC), part of the National Weather Service, issued its latest monthly ENSO diagnostic discussion on Oct. 8, 2026. It keeps an El Niño Advisory in effect, which means El Niño conditions are present and expected to continue.

The key numbers from that update:

• The Niño-3.4 index, which tracks sea surface temperatures in the central equatorial Pacific, stood at +2.1°C above normal.
• Readings farther east were even higher: +3.0°C in the Niño-3 region and +3.9°C in the Niño-1+2 region off South America.
• Most of those indices rose over the past month.

For context, the CPC's September discussion put the August Niño-3.4 reading at +1.8°C. The trend line has pointed upward all season.

Could this be the strongest El Niño on record?

The CPC now treats a record-setting event as more likely than not for the heart of the season. The agency defines a "historic" event as a three-month average on its relative index (RONI) of +2.5°C or higher, which would exceed any El Niño since 1950.

Separately, the CPC puts the chance of a strong-to-very-strong El Niño persisting through January–March 2027 at better than 83%. The agency's next update is scheduled for Nov. 12.

The CPC also offers a caution: a bigger event raises the odds of typical El Niño effects, but it does not guarantee them.

What are NASA satellites showing?

A NASA Science article published Oct. 15 traces the event back to January 2026, when a Kelvin wave, a slow pulse of warm water, was detected near Micronesia in the western Pacific. By early April those waves had reached the eastern Pacific and surface temperatures there began to climb.

According to NASA:

• Eastern Pacific waters are running roughly 3°F (1.7°C) above the long-term average.
• Heat-driven expansion of seawater has lifted sea level by about 30 to 40 centimeters in parts of the eastern Pacific, while levels near Indonesia and northern Australia sit about 15 to 20 centimeters below normal.
• The Sentinel-6 satellites map ocean height worldwide about every 10 days.
• NASA's PACE satellite, launched in 2024 and observing its first El Niño, shows equatorial waters turning bluer as phytoplankton decline, because weaker trade winds bring up fewer nutrients from the deep.

Josh Willis, a sea level project scientist at NASA's Jet Propulsion Laboratory, told NASA that Kelvin waves act "like the heartbeat of El Niño."

What does NOAA's winter outlook say for 2026-27?

NOAA released its U.S. Winter Outlook for December 2026 through February 2027 on Oct. 15. The agency says El Niño dominates the forecast.

Ken Graham, director of the National Weather Service, said in NOAA's release that the strong event will likely bring "a southward and eastward shift to the jet stream." That shift tends to steer more storms across the southern half of the country.

The outlook is expressed as probabilities, not guarantees. Here is how it breaks down by region:

"Equal chances" means forecasters see no strong tilt toward above-, near- or below-normal conditions.

What does El Niño mean for Boston and New England this winter?

NOAA's outlook does not carve out a separate forecast for New England. Boston falls within two broad zones the agency does name: much of the East, where a warmer-than-average winter is favored, and the East Coast, where wetter-than-average conditions are favored.

Historical patterns add some texture. A 2023 analysis on NOAA's Climate.gov by Michelle L'Heureux and Brian Brettschneider found that El Niño winters have tended to bring reduced snowfall around the Great Lakes and interior New England. The same analysis noted that moderate and strong events generally exert a larger effect on the atmosphere than weak ones.

That history comes with important caveats:

• It describes averages from past winters, not a forecast for this one.
• The authors noted that the Washington, D.C., area has sometimes seen above-average snow in El Niño years, even as other parts of the East saw less, a reminder that local outcomes vary.
• A wetter pattern along the coast can still produce significant snow if cold air is in place when a storm arrives.

Will Boston get more or less snow?

No one can say yet. NOAA states plainly that its seasonal outlook does not project snowfall totals, because snow generally cannot be predicted more than about a week ahead.

Instead, the National Weather Service points residents to shorter-range tools as storms approach, including a new Probabilistic Precipitation Portal that shows ranges and probabilities for snow, ice and rain. NOAA also says select blizzard and ice storm warnings will carry "Particularly Dangerous Situation" wording when forecasters have high confidence in a historic event.

What are the risks elsewhere in the country?

The same southward storm track that could ease drought in the Southwest, Southern Plains and Southeast also carries hazards. NOAA's Graham warned that heavy rain falling on dry ground can trigger destructive flash floods and mudslides, and urged communities to prepare early.

NASA notes that El Niño's reach extends beyond weather maps. Declining phytoplankton can ripple through marine food webs and push some sea life toward new feeding grounds, and the agency says farmers, firefighters and coastal communities are already feeling effects.

When will the forecast be updated?

Two dates matter for anyone tracking this winter:

• Nov. 12, 2026: The CPC's next monthly ENSO diagnostic discussion.
• Nov. 19, 2026: NOAA's next update to the three-month seasonal outlook.

Outlooks are refreshed monthly, so the picture for January and February could still shift.

Frequently asked questions

Is El Niño 2026 stronger than past events?

The Climate Prediction Center gives an 83% chance that the October–December 2026 period will qualify as a historic event, meaning stronger than any El Niño since 1950. That has not yet been confirmed. The final ranking depends on how the event evolves through the winter.

What is El Niño in simple terms?

El Niño is a periodic warming of surface waters in the central and eastern tropical Pacific Ocean. The warmth changes wind and rainfall patterns that can shift the path of the jet stream over North America. The Climate Prediction Center reports its strength using ocean temperature indices such as Niño-3.4.

Will this winter be warm in Boston?

NOAA's outlook favors a warmer-than-average December through February across much of the eastern United States, which includes Boston. That is a probability, not a promise, and cold snaps can still occur in a mild season.

Does El Niño mean less snow in New England?

A NOAA Climate.gov analysis found that El Niño winters have historically leaned toward less snow in interior New England. But NOAA does not forecast seasonal snowfall, and a wetter-than-normal East Coast pattern can still deliver big storms when cold air lines up.

How long will El Niño last?

The CPC says a strong-to-very-strong El Niño is likely to persist through at least January–March 2027. Forecasts beyond that are less certain and will be revisited in monthly updates.

Where can I find the latest El Niño forecast?

The Climate Prediction Center posts its monthly ENSO diagnostic discussion at cpc.ncep.noaa.gov, with the next due Nov. 12. NOAA's seasonal outlooks are also updated monthly, with the next issued Nov. 19.