What a very strong El Nino means

CPC says the high likelihood of a very strong El Nino is a major input to its fall and winter outlooks. The forecast shifts seasonal odds; it does not tell you what will happen in your town or in any particular week.

Source: NOAA Climate Prediction Center, Prognostic Discussion for Long-Lead Seasonal Outlooks, issued 17 September 2026.

Where things stand

CPC reports that El Nino conditions are present and strengthening.

CPC puts a 75% chance on OND meeting its historic-event threshold of +2.5 C or more for a three-month RONI value, and a greater than 90% chance of a very strong event during Northern Hemisphere fall and winter 2026-27. CPC says the chances of impacts consistent with El Nino are larger, but those impacts are not guaranteed.

What it tilts

CPC's September discussion describes these broad seasonal patterns. They are probabilities for three-month averages, not deterministic weather forecasts:

• Wetter across the southern tier. CPC puts the highest above-normal winter precipitation probabilities in the country over parts of the Southeast, where it says the teleconnections are strongest.
• Modestly drier over the interior Northwest and Great Lakes. CPC expects the below-normal precipitation signal to remain weak.
• Milder across the north. By winter, CPC's temperature pattern is dominated by above-normal probabilities over the west, north and east rather than the southern tier.
• Near-normal, not cold, in parts of the south. CPC indicates near-normal temperature chances over parts of the Southwest, the Southeast and the Lower Mississippi Valley, where a wetter, cloudier pattern offsets the long-run warming trend.

What it does not do

This is the part that gets lost between the forecast and the headline.

• It shifts odds. It does not schedule weather. A favoured category at 40% means the other two still hold 60% between them.
• Strong signal does not mean strong certainty. A very strong El Nino makes the seasonal tilt more reliable. It says nothing about any particular week.
• Seasonal averages hide the events that hurt. A winter can finish milder than normal and still deliver the ice storm, the cold snap, or the roof-loading snowfall. Plan for the extreme, not the average.
• No two El Ninos are the same. Other patterns run at the same time, and they can reinforce or cancel the signal regionally. CPC marks the places where the signals fight as equal chances rather than guessing.

So what should you actually do

Read the odds for your own region, then plan against your own normals rather than the national story. A mild-leaning winter in the Upper Midwest is still an Upper Midwest winter.

• Your regional outlook, with the numbers next to your station's normals.
• Your frost dates, which are normals and do not move with the seasonal forecast.
• Firewood and winter hay supply, both of which are sized off a normal season plus a margin, not off a forecast.

For how every other number on this site is computed and sourced, see the methodology.