What are the typical impacts of El Niño and La Niña on U.S. winter temperature anomalies?
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Executive summary
La Niña typically tilts U.S. winter temperature anomalies colder in the northern and north‑central states and warmer/drier in the southern tier, while El Niño tends to shift warmth and wetness into the southern U.S. and relative cooling in parts of the north — forecasts and historical composites underpin these general patterns (NOAA/Climate.gov; WeatherBug) [1] [2]. Current 2025–26 outlooks from NOAA, WMO and media note a weak La Niña favored for winter with probabilities ranging roughly 54–71% for parts of the season, but agencies caution many regions may still run above normal because of long‑term warming [3] [4] [5].
1. What the textbooks say: the canonical ENSO–winter temperature pattern
Climate scientists and federal agencies describe a consistent statistical association: El Niño shifts the Pacific jet southward, usually producing warmer‑than‑average conditions across the southern U.S. and increased winter warmth risk in portions of the northern tier; La Niña often produces the opposite — colder anomalies across the north and north‑central U.S. and warmer/drier conditions across much of the South (NOAA/Climate.gov; WeatherBug) [1] [2].
2. How big are the signals — and when do they matter?
ENSO is a leading seasonal driver but not a deterministic switch. Composited maps from strong events show clearer temperature departures (e.g., for strong El Niños wetter‑warmer signals in the southern tier), yet the size and location of anomalies vary by event and by strength; forecasters therefore treat ENSO as an important but probabilistic influence on winter temperatures (NOAA/Climate.gov; Weather.gov) [1] [6].
3. The real world complicates the story: competing drivers and recent trends
Seasonal outlooks explicitly include other factors — the Arctic Oscillation, North Atlantic variability and long‑term warming — that can amplify, mute or even reverse typical ENSO patterns. NOAA and the National Weather Service warn that these high‑latitude modes and background climate trends often alter the realized winter outcome, so ENSO’s “typical” fingerprints do not always appear as expected [6] [1].
4. What recent winters teach us: exceptions and surprises
Long‑record analyses show notable exceptions: strong El Niño winters such as 2015–16 did not uniformly match the textbook precipitation or temperature maps in every region, and a La Niña following a warm El Niño winter can still leave many areas warmer than climate normals because of global background warming (NOAA/Climate.gov; Forbes) [1] [7]. Recent operational assessments stress that while La Niña tends to cool the north, many U.S. regions remain at risk of above‑normal temperatures overall [5] [7].
5. The current (2025–26) operational outlook — what forecasters are saying now
NOAA’s Climate Prediction Center and allied reporting in late 2025 favored a La Niña influence on winter 2025–26, with agencies and outlets citing probabilities from roughly the mid‑50s to low‑70s percent for La Niña conditions in different windows (e.g., 71% for Oct–Dec in some reports; 55% probability for Dec–Feb from WMO) [4] [3] [5]. Forecasters emphasize that a weak La Niña is expected, and its expected signal is most pronounced in precipitation patterns and in colder than normal temperatures across the north‑central U.S. while much of the South trends drier and warmer [2] [8].
6. How to interpret seasonal temperature outlooks as a consumer or planner
Treat ENSO‑based forecasts as probabilistic nudges, not guarantees. Historical composites give likelihoods of above‑ or below‑normal temperatures in broad regions — useful for planning — but local outcomes can differ because of other atmospheric variability and long‑term warming. NOAA, WeatherBug and media coverage all emphasize that ENSO’s presence raises the odds of certain patterns (e.g., colder north under La Niña) but does not lock in specific daily weather events [1] [2] [6].
7. Sources, caveats and the limits of current reporting
This summary relies on NOAA/Climate.gov guidance and contemporary reporting and outlooks from WeatherBug, WMO, Newsweek and related media that interpreted CPC/WMO probabilities and composite patterns [1] [2] [5] [4]. Available sources do not quantify a single, nation‑wide average temperature anomaly tied exclusively to El Niño or La Niña for a given winter; instead they present regional likelihood shifts and probabilistic forecasts (not found in current reporting). Forecasters also highlight that ENSO strength matters: weak events produce weaker, less predictable signals than strong ones [9] [2].
Bottom line: ENSO biases winter temperatures in predictable regional ways — La Niña favors cooler winters across the north and warmer/drier conditions in the South; El Niño tends to favor southern warmth and wetness — but real outcomes depend on ENSO strength, concurrent atmospheric patterns and the steady upward pressure of background climate warming [1] [2] [5].