The short version
The September 17 CPC outlook still relies heavily on the high probability of a very strong El Niño. For October–December, above-normal temperatures are favored across much of the West, northern tier and East, while above-normal precipitation is favored from Southern California and the Four Corners through the Plains, Mississippi and Tennessee Valleys, Southeast and Mid-Atlantic.
1. Great Lakes and Northeast warmth expanded eastward
CPC says 40–50% probabilities favoring above-normal temperatures were extended eastward across the Great Lakes and Northeast for OND. This matters for snow because an active storm pattern can still produce more rain or mixed precipitation when temperatures are marginal.
2. The southern wet corridor remains the dominant precipitation signal
For OND, CPC favors above-normal precipitation from the southern half of California across the Four Corners and much of the Great Plains, Mississippi and Tennessee Valleys, Southeast and Mid-Atlantic. The highest OND wet probabilities exceed 60% in parts of the eastern Gulf Coast and Southeast.
3. California’s wet signal strengthens deeper into winter
From DJF through FMA, CPC says coastal California wet probabilities reach roughly 50–60%. That supports a meaningful seasonal rain signal for cities such as Los Angeles, San Francisco and San Diego, while mountain snow still depends on storm temperature and elevation.
4. Southeast wet odds become especially strong
Later in winter, CPC describes 70–80% probabilities of above-normal precipitation around southern Georgia and northern Florida. Core-winter temperatures across much of the Southeast are closer to near normal because cooler El Niño influence competes with warmer historical trends.
5. A negative PDO is a real complication
The August PDO index was −1.11. CPC notes that the three famous very strong El Niño events since 1950 occurred with a positive PDO, while the current negative phase may damp some typical strong-El Niño impacts in certain regions. CPC specifically tempered coastal Pacific Northwest warm probabilities in response.
6. Great Lakes and interior Northwest dry signals remain modest
CPC keeps modest below-normal precipitation tilts over parts of the interior Northwest and Great Lakes through much of winter. These are weaker signals than the southern wet corridor, so they should not be treated as guarantees of a dry season.
What happens next
The next ENSO Diagnostic Discussion is scheduled for October 8, 2026, and the next CPC long-lead seasonal outlook release is scheduled for October 15, 2026. We will compare those releases with this one rather than silently overwriting the history.
Primary source: NOAA CPC Prognostic Discussion for Long-Lead Seasonal Outlooks, issued September 17, 2026 ↗.