What La Niña or El Niño conditions are forecast for Dec 2025–Jan 2026 and how will they influence North American weather?
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Executive summary
Most operational forecasting groups in November–December 2025 favored a weak La Niña for the December 2025–February 2026 season, with probabilistic models putting La Niña chances roughly in the 50–67% band and a shift toward ENSO‑neutral likely by Jan–Mar 2026 (examples: IRI 53% for Dec–Feb; CPC/NCEP “La Niña Advisory” with ~55–68% chance of neutral by Jan–Mar) [1] [2] [3]. Agencies and media warn that a lingering La Niña influence will tend to favor wetter-than-normal Pacific Northwest and drier‑warmer conditions in parts of the Southwest, southern Plains and Southeast through winter, though model confidence drops after winter and some groups project a neutral or possible El Niño later in 2026 [4] [5] [6].
1. What the official forecasts say right now
NOAA’s Climate Prediction Center issued a La Niña Advisory and judged La Niña favored to continue into December 2025–February 2026 while assigning a strong likelihood of transition to ENSO‑neutral in the January–March 2026 window (CPC gives about a 55–68% chance of neutral by Jan–Mar) [2] [3]. The International Research Institute’s multimodel plume shows La Niña probability about 67% for Nov–Jan, easing to about 53% for Dec–Feb 2025/26, with neutral becoming the dominant outlook from January–March onward [1].
2. How consistent are other groups and private analysts?
Independent forecasters and industry outlets largely mirror the official call: some label the event “weak” La Niña and expect it to persist into early 2026 before neutral takes over (Climate Impact Company, SkyMet, WMO summaries) [6] [7] [8]. A few long‑range products and model ensembles hint at El Niño risk later in 2026, but those projections carry higher uncertainty and are not the current operational consensus [9] [10].
3. What “La Niña” means for North American winter patterns
Historical La Niña teleconnections typically shift the jet stream and storm tracks so the Pacific Northwest, Intermountain West and Ohio Valley see above‑average precipitation and cooler temperatures, while the Southwest, southern Plains, Southeast and parts of California trend drier and warmer. U.S. drought outlooks in late 2025 flagged potential drought persistence in the Southwest and improvement in the Pacific Northwest under the La Niña signal [4]. Major outlets and NOAA’s briefing repeated similar regional impacts for winter 2025–26 [5] [4].
4. Strength and timing matter — why this La Niña is described as “weak”
Several analyses emphasize this La Niña is marginal or weak: sea‑surface anomalies were near La Niña thresholds (e.g., Niño3.4 near −0.4 to −0.5°C in autumn), and models produce only modest cooling, so atmospheric responses may be muted and short‑lived (examples in SkyMet and CIC briefings) [7] [6]. A weak event can still shift seasonal odds, but it produces less deterministic outcomes than a strong La Niña and allows other drivers (Madden–Julian Oscillation, stratospheric warming, background ocean warming) to modulate weather [9].
5. Where forecasts disagree or carry big uncertainty
Model spread is the story: ensemble probabilities range (IRI’s 53–67% vs. WMO/NOAA ~55–71% windows cited by media), and most centers stress higher uncertainty beyond late winter. Several groups explicitly state that a transition to ENSO‑neutral is likely by Jan–Mar 2026, and some extended forecasts show an El Niño risk in mid‑2026 — but that is low‑confidence and subject to the spring predictability barrier [1] [2] [9].
6. What that means for planning and impacts this winter
Operational agencies and regional forecasters recommend treating the season as La Niña‑tilted: elevated odds of a wetter Pacific Northwest and a drier Southwest and southern Plains, with potential implications for water resources, wildfire risk, and agriculture. News coverage and national briefings echo those risk shifts while warning that local weather always varies and that the La Niña signal weakens if neutral returns in early 2026 [5] [4] [8].
Limitations and transparency: forecasts cited here come from public NOAA/CPC, IRI, WMO summaries and a set of private forecasters and media reports; all note substantial model spread and reduced certainty beyond winter 2025–26 [2] [1] [8]. Available sources do not mention precise local outcomes for every U.S. state — use regional NWS and state climate offices for fine‑scale winter guidance.