The Current La Niña Signal Is Two Months Old – A Full-fledged La Niña Unlikely During The 2025–26 Winter Season

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Enso Status on 5th January 2026

By the end of December 2025, the ongoing La Niña signal is two months old. Based on the forecast trend of Niño-3.4 sea surface temperature anomalies, the development of a full-fledged La Niña during the remaining part of the Indian winter season appears unlikely and, in practical terms, not possible. With the Indian winter concluding by February 2026, there is insufficient time for the required persistence of La Niña conditions to be achieved.

Few Agencies are even indicating a shift towards El Niño during 2026. However, it is too early since the current La Niña thresh hold should first change to Enso neutral.

Current ONI Status

Two consecutive La Niña thresholds have been attained so far:

• SON 2025 (September–October–November): ONI = –0.5 °C

• OND 2025 (October–November–December): ONI = –0.5 °C

These values confirm that La Niña threshold conditions have been met for two overlapping three-month seasons.

NOAA Criteria for a Full-Fledged La Niña

According to criteria defined by NOAA, a full-fledged La Niña event requires five consecutive overlapping three-month periods with ONI values at or below –0.5 °C.

With SON and OND 2025 accounting for the first two qualifying periods, the remaining three seasons—NDJ, DJF, and JFM (2025–26)—would also need to maintain La Niña threshold conditions. Current forecasts do not support such sustained cooling through all these periods.

ONI data referenced in this analysis are sourced from the Climate Prediction Center of CPC under the U.S. National Weather Service (NWS).

Important Note on ONI Revisions

The CPC has recently updated its climatological base period to 1996–2025 as part of its routine five-year revision cycle. This revised climatology was formally adopted in January 2026 and has resulted in minor revisions to recent ONI values.

Final Take

Based on the updated climatology and NOAA’s official classification criteria, it is expected that the Indian winter of 2025–26 (December 2025 to February 2026) will conclude before a full-fledged La Niña is recorded, if it can materializes at all. Although two La Niña thresholds have been briefly achieved, forecasts indicate that these conditions are unlikely to persist for the required five consecutive overlapping three-month seasons. Consequently, from both a historical and operational perspective, this period is expected to be classified as ENSO-neutral.

The Climate Prediction Center (CPC) is a division of NOAA’s National Centers for Environmental Prediction (NCEP).

Latest Oceanic Nino Index Graph Shows Two La Nina
Thresh Hold Achieved At The End Of December 2025

The Table below shows the monthly SST of Nino3.4 Region and the Climate adjusted normal SST and SST anomaly from April 2024. Recently revised Climate Base 1996-2025. ERSST.v5

Period    Nino3.4 ClimAdjust
YR   MON  Temp.ºC Temp.ºC ANOM ºC


2024   4   28.60   27.71    0.89
2024   5   28.17   27.83    0.34
2024   6   27.90   27.67    0.23
2024   7   27.34   27.25    0.09
2024   8   26.74   26.81   -0.07
2024   9   26.46   26.68   -0.22
2024  10   26.45   26.67   -0.22
2024  11   26.46   26.65   -0.19
2024  12   26.00   26.50   -0.49
2025   1   25.82   26.38   -0.56
2025   2   26.33   26.61   -0.28
2025   3   27.30   27.19    0.11
2025   4   27.69   27.71   -0.02
2025   5   27.80   27.83   -0.02
2025   6   27.66   27.67   -0.01
2025   7   27.15   27.25   -0.10
2025   8   26.49   26.81   -0.32
2025   9   26.25   26.68   -0.43
2025  10   26.22   26.67   -0.45
2025  11   26.01   26.65   -0.64
2025  12   25.94   26.50   -0.56

Indications and analysis of various International Weather/Climate agencies monitoring Enso conditions is depicted hereunder:

Summary by: Climate Prediction Center / NCEP  Dated 29th December 2025

ENSO Alert System Status: La Niña Advisory

La Niña is present.*
Equatorial sea surface temperatures (SSTs) are below average across the East central and Eastern Pacific Ocean.
Atmospheric anomalies over the tropical Pacific Ocean are consistent with La Niña.
La Niña is favored to continue for the next month or two, with a transition to ENSO-neutral most likely in January-March 2026 (68% chance).*

Note: Statements are updated once a month (2nd Thursday of each month) in association with the ENSO Diagnostics Discussion, which can be found by clicking here.

Recent (preliminary) Southern Oscillation Index values as per The Long Paddock – Queensland Government.

30 Days average SOI was -1.47 at the end of December 2025 and was +3.95 on 4th January 2026 as per The Long Paddock – Queensland Government and 90 Days average SOI was +8.05 on 4th January 2026. The monthly values are in neutral zone.

As per BOM – Australia 23rd December 2025

• La Niña continues in the tropical Pacific. The weekly Niño3.4 SST index was −0.91 °C for the week ending 21 December 2025, consistent with La Niña, with values fluctuating near the threshold since mid-to-late September. Atmospheric indicators—including trade winds, pressure, and cloud patterns—have consistently supported La Niña conditions. While the 30-day SOI briefly fell to −0.1 due to recent tropical activity near Tahiti, the 60-day and 90-day SOI values (+7.0 and +6.6) remain near La Niña levels. BOM models indicate La Niña is likely to persist into early 2026 before returning to neutral, earlier than the typical ENSO decay and broadly in line with international guidance.

  BOM has introduced Relative Niño indices

  
  

The details about Relative Index is here