How will el niño or la niña influence weather patterns in december 2025 and january 2026
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Executive summary
Forecasters in late 2025 overwhelmingly expect a weak La Niña to influence December 2025–January 2026, with most agencies giving La Niña a better‑than‑even chance for the Dec–Feb period (roughly 53–67% in model plumes and 55% in WMO statements) and a likely transition back to ENSO‑neutral by early 2026 (around 61–68% chance) [1] [2] [3] [4]. That weak La Niña is expected to nudge seasonal temperature and precipitation patterns — for example, raising chances of drier, warmer conditions across parts of the U.S. Southwest and Southeast and wetter, cooler tendencies in the Pacific Northwest and Ohio Valley — but forecasts stress the event is weak and not guaranteed, so local outcomes will vary [5] [6] [7].
1. La Niña is the working forecast; odds and timing matter
Operational centers and multimodel plumes in November–December 2025 place a clear but not overwhelming probability on La Niña persisting into the heart of winter: the IRI plume and many models give ~53–67% for Dec–Feb or Nov–Jan windows, WMO cites ~55% for Dec–Feb, and NOAA/CPC’s advisory favors La Niña continuing through December with transition to ENSO‑neutral most likely in January–March 2026 [1] [8] [2] [3]. That means forecasters treat La Niña as the dominant signal for December and probably January, but expect a weakening and return to neutral by early 2026 [2] [6].
2. Typical La Niña fingerprints for winter weather — where effects are most consistent
Historical La Niña winters tend to bias seasonal patterns: across the contiguous U.S., La Niña increases the chance of below‑average precipitation and above‑average temperatures in the Southwest, Southeast, Southern California and Texas, while favoring above‑average precipitation and below‑average temperatures for the Pacific Northwest, Intermountain West and parts of the Ohio Valley (NOAA/PSL analysis summarized by Drought.gov) [5]. Seasonal outlooks issued by CPC and others similarly favor warmer-than-normal areas across much of the East Coast, Southeast and Southwest for DJF 2025–26, with cooler signals in parts of the Upper Midwest and northern plains consistent with a La Niña tendency [6].
3. A weak La Niña moderates but does not eliminate surprises
Multiple sources emphasize this La Niña is expected to be weak; a weak event generally produces weaker and less deterministic impacts than a strong one [9] [6]. WMO and press reporting caution that even with La Niña’s cooling influence, global and regional temperatures can remain above normal because of long‑term warming, and non‑ENSO drivers (like the Madden‑Julian Oscillation, stratospheric events or regional ocean anomalies) can produce “oddball” weather that departs from the canonical pattern [8] [3] [10] [11].
4. What to expect month‑by‑month: December 2025 and January 2026
For December 2025, forecasters expect La Niña to be the more likely state and therefore for its typical winter fingerprints to be active — e.g., enhanced odds of drier/warmer conditions for the U.S. South and Southwest and wetter/cooler signals in the Pacific Northwest and parts of the Midwest [5] [7]. By January 2026, model guidance and CPC/IRI plumes show La Niña weakening and ENSO‑neutral becoming increasingly likely in the Jan–Mar window (roughly 61–68% chance of neutral by Jan–Mar), so La Niña’s influence should wane through January with growing uncertainty about mid‑winter persistence [2] [6] [1].
5. Regional caveats and practical implications
Impacts differ by region and by strength: in the U.S., the biggest practical signals are drought risk increases across the Southwest/Southern Plains and a higher Atlantic hurricane likelihood earlier in the season when La Niña is present — but reporting stresses this La Niña’s weak intensity reduces the magnitude of those odds and local weather systems often override seasonal tendencies [12] [5] [9]. Outside the U.S., agencies (WMO, IRI, national centers) note La Niña increases odds of altered rainfall and temperatures regionally but that outcomes depend on interacting patterns such as the Indian Ocean Dipole or intraseasonal variability [13] [11].
6. Where forecasters disagree and why you should care
Sources agree on a weak La Niña emerging for winter 2025–26 but differ slightly on probabilities and timing: some model plumes place La Niña probability above 60% for Nov–Jan [1] [9], WMO and Phys.org lean ~55% for Dec–Feb [3] [4], and NOAA/CPC places higher odds on a Jan–Mar transition to neutral [2] [6]. The disagreement reflects natural forecast uncertainty, model spread and rapidly changing ocean‑atmosphere conditions — meaning users should treat seasonal guidance as probabilistic risk information, not deterministic weather forecasts [1] [2].
7. Bottom line for planners and the public
Expect La Niña to be the leading climate signal for December 2025 and into January 2026, biasing seasonal odds toward the classic La Niña patterns (drier/warm in parts of the U.S. South/Southwest, wetter/cooler in the Northwest), but prepare for a weakening signal and transition to ENSO‑neutral in early 2026 that will increase uncertainty [5] [2] [3]. For precise travel, water‑resource or agricultural decisions, consult local seasonal outlooks and updates from NOAA/CPC, WMO and regional forecast centers, because a weak La Niña produces only modest shifts in probabilities and local weather will still be driven by shorter‑term systems [2] [8].
Limitations: this analysis draws only on the listed late‑2025 forecasts and summaries; available sources do not mention detailed local forecasts for every country or sub‑region beyond the cited summaries [1] [2] [5].