Seasonal outlooks for Autumn/Winter 2025–2026

Published: August 29, 2025
by Whatweather.today

Autumn/Winter 2025–2026: A science-based outlook distilled from today’s strongest climate signals

We can’t script the weather months in advance, but we can read the larger “gears” that steer it. This consolidated outlook blends the best insights from two in‑depth drafts into one clear, science‑grounded guide. It isn’t a day‑by‑day forecast; it’s a practical synthesis of the major climate drivers most likely to shape the character of autumn 2025 and winter 2025–26 across North America, Europe, East Asia, and key regions around the globe.

Think of it as a probability map. ENSO in the tropical Pacific, the polar vortex over the Arctic, the NAO/AO over the Atlantic, the MJO’s intraseasonal pulse, and the warm global baseline from climate change together nudge the dice toward certain seasonal flavors. Your best strategy is to use these signals for medium‑range planning—and then lean on short‑term, local forecasts as the season approaches. For location‑specific updates anytime, keep a quick local check handy with a reliable Weather Forecast: https://whatweather.today.

What seasonal outlooks can and can’t do

  • Where they help:
    • Identify risk tilts (warmer/colder, wetter/drier) over broad regions, especially when the tropics are driving strongly (e.g., a clear ENSO phase).
    • Flag periods when storm tracks and heavy‑precipitation events are more likely.
  • Where they can’t:
    • Pinpoint exact storm tracks, snowfall totals, or cold outbreak timing months ahead.
    • Predict the NAO/AO or sudden stratospheric warming events beyond a few weeks with reliability.
  • How to use them:
    • Plan around scenario‑based risks, revisit monthly as new observations arrive, and pivot to week‑to‑week guidance in season. For day‑to‑day decisions, use an updated Weather Forecast: Weather Forecast.

The foundational backdrop: a warmer, wetter‑extremes climate

Recent years have run hot, with exceptional ocean warmth and high global temperatures. This warmer baseline matters because:

  • Warmer air holds more moisture: About 7% more per +1°C, raising the ceiling on rainfall and snowfall rates when storms tap deep moisture.
  • Marine heatwaves: Supercharge latent heat availability, often intensifying atmospheric rivers and extratropical cyclones.
  • Warm North Atlantic: Can energize the autumn storm track and interact with the NAO, though the exact NAO phase remains largely governed by internal variability.

Bottom line: Regardless of the circulation regime, the background climate now tilts toward heavier precipitation extremes when and where storms occur, and toward milder seasonal averages—even if sharp cold snaps still happen.

ENSO: the hinge driver into 2025–26

ENSO (El Niño–Southern Oscillation) modulates the jet streams by shifting tropical convection. After a strong 2023–24 El Niño and an anticipated La Niña through 2024–25, late‑2025 plausibly presents three ENSO states:

  • Scenario A — Lingering La Niña (weak to moderate)
    • North America: Cooler/wetter risk from the Pacific Northwest through the northern Rockies/Plains into the Great Lakes; warmer/drier tilt across the southern tier (Southwest → Gulf Coast → Florida).
    • Europe: Statistical lean toward a more positive NAO (milder/stormier NW Europe, drier Mediterranean), but this link is weaker and often overshadowed by internal variability and stratospheric influences.
    • Indo‑Pacific: Greater risk of cold surges into East Asia; La Niña often favors wetter Australia, modulated strongly by the IOD.
  • Scenario B — ENSO‑neutral
    • Weaker tropical teleconnections hand more control to the MJO, NAO/AO, and the stratospheric polar vortex.
    • Outcomes swing more: bursts of storms or cold snaps punctuate otherwise mild spells.
  • Scenario C — Return to El Niño (less likely immediately but possible)
    • North America: Strengthened subtropical jet and wetter‑than‑normal risk across the southern U.S. and California; northern tier often leans warmer/drier.
    • Global rainfall belts: Shift, with region‑specific impacts in the Indo‑Pacific and South America.

Given the sequence through 2024–25, Scenarios A and B are the most climatologically plausible for late 2025, pending updated ENSO observations by mid‑2025 (Niño‑3.4 index, subsurface heat content, trade winds).

The Arctic wild card: polar vortex, AO/NAO, and SSWs

The stratospheric polar vortex (SPV) is a cold, cyclonic circulation over the Arctic during winter. When strong and stable, it corrals the cold; when disrupted—especially after a Sudden Stratospheric Warming (SSW)—the jet stream can buckle, sending Arctic air surging into mid‑latitudes.

  • Arctic sea ice: Early‑season refreeze patterns can affect surface fluxes and wave activity into the stratosphere.
  • Quasi‑Biennial Oscillation (QBO): Modulates SSW likelihood; easterly phases have historically coincided with more frequent/weaker SPV episodes.
  • NAO/AO: Reflect surface pressure patterns linked to jet latitude/strength; negative phases elevate cold/snow risk in parts of Europe and the eastern half of North America.

What we can say: Major SSWs occur in many winters. If one materializes in 2025–26, its impacts can override ENSO for several weeks, boosting cold‑outbreak and snow potential downwind.

Other drivers you shouldn’t ignore

  • Indian Ocean Dipole (IOD): Peaks in boreal autumn. Positive IOD favors East African short‑rains enhancement and Australian dryness; negative IOD often does the reverse.
  • Madden–Julian Oscillation (MJO): A 30–60 day tropical pulse that, depending on phase, can precede West Coast atmospheric rivers or central/eastern U.S. cold spells, and trigger East Asia cold surges.
  • North Atlantic SST patterns: Tripole configurations can bias storm tracks and interact with the NAO timing.
  • Eurasian snow cover (October): Linked in some studies to later negative AO risk, but with year‑to‑year variability.

Quick scenario matrix

Scenario ENSO state North America Europe Indo‑Pacific & Australia Notes
A La Niña Cooler/wetter north; warmer/drier south Lean positive NAO: mild/stormy NW, drier Med (low confidence) East Asia cold surges; Australia wetter if IOD/La Niña align Atmospheric rivers into PNW more frequent
B Neutral Highly variable; MJO/NAO/SSW drive swings NAO‑dependent: mild/wet vs. blocked/cold flips MJO steers bursts of rain/cold surges; outcomes swing Greatest intraseasonal volatility
C El Niño Wetter south/California; warmer/drier northern tier Signal weaker; often altered storm tracks Australia/Indonesia tilt drier; regional shifts Historically less likely immediately after La Niña

Autumn 2025 (SON): how the stage sets

  • If La Niña is present:
    • North America: Active Pacific jet into the Pacific Northwest; wetter‑than‑normal risk there; southern tier leans warmer/drier; early mountain snow more likely in the interior Northwest/northern Rockies.
    • Tropics: Western Pacific cyclones track farther west on average; if the Atlantic remains warm, late‑season activity can linger.
    • Australia/Indonesia: Increased spring rainfall and flood risk under La Niña; the IOD phase can amplify or offset this.
    • Europe: A lively North Atlantic storm track toward the British Isles/Scandinavia under a positive NAO; southern Europe can lean drier.
  • If ENSO‑neutral:
    • North America: Big swings—MJO phases may cue atmospheric river bursts or early cold shots.
    • Europe: Storm track is more free to wander; week‑to‑week NAO changes govern mild/wet versus early cold spells.
    • IOD‑sensitive regions: East African short rains and Australian spring rainfall hinge more on IOD polarity.

Across scenarios, the warm baseline means heavier rain potential when storms line up, especially in atmospheric rivers and slow movers.

Winter 2025–26 (DJF): what each scenario implies

  • Scenario A — La Niña winter
    • North America — Temperatures: Cooler risk north (PNW → northern Plains/Great Lakes); warmer south (Southwest → Gulf → Florida).
    • North America — Precipitation: Wetter PNW/northern Rockies and parts of the Ohio/Tennessee Valleys; drier tilt in the Southwest/Gulf/Florida. Northern Sierra fares better than southern Sierra on average in La Niña.
    • North America — Hazards: Frequent atmospheric rivers into the PNW; periodic Arctic outbreaks into the central/eastern U.S., especially if AO turns negative for multi‑week stretches.
    • Europe: If NAO stays positive, expect milder, stormier NW Europe and a drier Mediterranean. An SSW‑driven NAO flip could deliver notable cold/snow spells in central/eastern Europe.
    • East Asia: Enhanced cold surge risk and snow along Japan’s Sea of Japan snowbelts; wetter tendencies into parts of Southeast Asia.
    • Southern Hemisphere/tropics: Australia often runs wetter during La Niña summers, with elevated flood risk—conditional on IOD evolution and local blocking.
  • Scenario B — ENSO‑neutral winter
    • North America: Teleconnections weaken; the MJO and stratospheric events loom large. Expect a “whiplash” feel: mild interludes punctuated by sharp cold snaps and storm windows.
    • Europe: NAO‑driven: Prolonged positive NAO spells bring mild, wet NW Europe and drier Mediterranean; sustained negative NAO spells boost cold/snow potential and wetter Iberia/Mediterranean tracks.
    • East Asia: Cold surge frequency and snowfall hinge on SPV stability and MJO timing; variability is the rule.
  • Scenario C — Return to El Niño
    • North America: Stronger subtropical jet favors wetter south and California; reduced cold risk in the southern tier; northern tier often leans warmer/drier.
    • Europe: Signal varies and is typically weaker than NAO influences; localized outcomes depend on jet latitude shifts.
    • Indo‑Pacific: Heightened drought risk in Australia/Indonesia during El Niño summers; rainfall redistribution across the Pacific and South America.

Regional snapshots for planners

  • Western North America
    • Risks: Atmospheric rivers, landslides on steep/burn‑scar terrain, volatile mountain snowpack.
    • Watch: Niño‑3.4 SSTs; MJO phases 7–8 (West Coast storm risk); Pacific jet latitude/strength.
  • Central/Eastern North America
    • Risks: Arctic fronts and ice storms when AO goes negative; Ohio/Tennessee Valley flood potential in La Niña years.
    • Watch: AO/NAO daily trajectories; soil moisture and antecedent flood conditions.
  • Europe
    • Risks: Windstorms/flooding in NW Europe under positive NAO; cold/snow bursts in central/eastern Europe under negative NAO/SSW influence; Mediterranean drought vs. flood swings.
    • Watch: NAO index, North Atlantic SST tripole, 10 hPa zonal winds (SPV health).
  • East Asia and the Western Pacific
    • Risks: Enhanced snowfall along the Japan Sea side; river flooding in parts of SE Asia if La Niña persists; air‑quality issues under stagnant highs.
    • Watch: ENSO status, Siberian high strength, MJO phases 5–7 (often precede cold surges).
  • Australia and the Indo‑Pacific
    • Risks: Flooding if La Niña/negative IOD align; drought/fire if El Niño/positive IOD prevail.
    • Watch: IOD index (BoM), ENSO updates, soil moisture, heatwave outlooks.
  • Africa and South America
    • East Africa: Positive IOD favors enhanced OND “short rains”—monitor for flood risk.
    • Amazon and northern South America: ENSO shifts rainfall; neutral/La Niña often favor more DJF rainfall over parts of the basin; El Niño tends to suppress it.

Hazards and extremes: physics‑driven expectations

  • Heavier precipitation: A warmer atmosphere juiced with oceanic moisture raises top‑end rainfall rates during atmospheric rivers and slow‑moving lows.
  • Snow and ice: When cold air coincides with deep moisture, snowfall can still be intense; the snowline may oscillate more, complicating hydrology and avalanche risk.
  • Windstorms: With an energized Atlantic in autumn, expect vigorous cyclones in NW Europe; track and intensity respond to SST gradients and jet structure.
  • Drought/heat: Enhanced evaporative demand during dry spells intensifies drought risk, particularly across the southern U.S., Mediterranean, and parts of Australia depending on ENSO/IOD and blocking.

What to monitor through late 2025

  • ENSO metrics: Niño‑3.4 SST anomalies and subsurface heat content (NOAA CPC). A sustained −0.5 to −1.0°C favors lingering La Niña; hovering near zero suggests neutral.
  • IOD index (Australian BoM): Crucial for SON rainfall across Australia/Indonesia/East Africa.
  • North Atlantic SSTs (NOAA OISST/C3S): Tripole patterns can bias the NAO and storm vigor.
  • MJO phase/amplitude (NOAA CPC): Phases 7–8 often cue West Coast storms; 2–3 can precede eastern North America cold; 5–7 often precede East Asia cold surges.
  • Stratospheric diagnostics (CPC): Watch 10 hPa zonal winds and heat flux; SSWs often preface increased mid‑latitude cold/snow risk within 1–3 weeks.
  • Arctic sea ice (NSIDC) and Eurasian snow cover (Rutgers): Autumn evolution can subtly influence winter circulation tendencies.

Practical planning tips

  • Blend horizons: Use this scenario guide for seasonal risk posture; then shift to week‑ahead synoptics and day‑of nowcasting for decisions. A quick daily check helps: https://whatweather.today.
  • Prepare for swings: Neutral/weak ENSO winters often feature “weather whiplash.” Build slack in schedules and supply chains for 1–2 week disruption windows.
  • Water management: Clear debris basins and check reservoirs ahead of atmospheric river season in West Coast regions with wetter tilts; update flood plans where soils are saturated.
  • Energy and heating: Expect higher load variability; stress‑test for sudden cold snaps even in generally mild winters.
  • Agriculture: Use probabilistic outlooks for crop and irrigation planning; adjust in season to MJO/NAO updates.

Uncertainty and confidence

  • Higher confidence:
    • Warm baseline and enhanced heavy‑precipitation potential when storms occur.
    • Canonical ENSO teleconnections if La Niña persists into late 2025.
  • Lower confidence:
    • NAO/AO phase beyond ~2 weeks, timing/magnitude of SSWs, and specific storm track evolution months in advance.

Keep this outlook “alive” by revisiting monthly. Reassess ENSO/IOD by mid‑2025, watch North Atlantic SST anomalies and early storm‑track signals in September–October, and monitor the stratosphere and AO/NAO from late November onward. If La Niña persists, expect a familiar tilt: wetter PNW, drier southern U.S., and a mild, stormy NW Europe tendency—interrupted at times by cold shots if the AO flips negative. If the Pacific settles near neutral, prepare for bigger swings where intraseasonal drivers and the stratosphere call the tune.

Bottom line

  • Autumn/winter 2025–26 will likely unfold on a warmer global canvas that elevates heavy‑rain potential and softens the depth/duration of most cold spells—but not all.
  • ENSO’s late‑2025 state is the hinge. A lingering La Niña favors classic patterns across North America and modulates risks in the Indo‑Pacific; neutral hands more control to the MJO and stratosphere.
  • Europe’s story remains tightly tied to the NAO/AO and the health of the polar vortex; a single SSW can tip the balance toward multi‑week cold.
  • Best practice: plan by scenario, verify monthly, and act on short‑term updates. For local, up‑to‑the‑minute checks, use a fast daily forecast tool: https://whatweather.today.
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