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Oceanic Niño Index — Monthly Sea Surface Temperature Anomaly

NOAA's Oceanic Niño Index (ONI): the three-month running mean of sea surface temperature anomalies in the Niño 3.4 region of the central equatorial Pacific (5°N–5°S, 120°–170°W), in degrees Celsius. Positive values indicate El Niño-like warmth, negative values La Niña-like cooling.

ArchiveFrom before CK Economics turned to global trade on October 16, 2026. Its figures are still collected and it stays at this address, but it is no longer part of our trade coverage.

Data status: Current
Official statisticCK forecastSource figures as of October 10, 2026 · Autoregression, 2 years, 80% range of backtest errorsSources & methods
Sources
NOAA Climate Prediction Center
Period covered
Jan 1950 – Aug 2026
Source figures as of
October 10, 2026
Geography
Niño 3.4 region, equatorial Pacific (5°N–5°S, 120°–170°W)
Sector
Climate Economics & Sustainability (archived)
Seasonal adjustment
Not applicable
Transformations
Views other than the level (changes, averages, volatility) are calculated by CK Economics from these figures
Forecast method
Autoregression
Assumptions
Past patterns continue, with no policy change or shock; fitted to Jan 1950 – Aug 2026
Horizon
2 years
Interval
80% range of backtest errors
Backtest
Errors 39% smaller than a no-change forecast over the next 3 months, 37% smaller 1–2 years ahead (40 past dates)
Estimated
October 16, 2026
Revisions
Replaced with the source’s latest figures whenever it revises them.
Data status
Current

Full method · Research standards

Key figures

CK estimate°C anomaly · calculated by CK Economics from NOAA National Weather Service data

Latest · Aug 2026
2.16
+2.4 °C vs a year earlier1
5-year change
+2.6 °C
since Aug 20212
10-year change
+2.5 °C
since Aug 20162
Record high
2.59
Dec 20153
Record low
−2.04
Dec 19733
Where the latest ranks
99th pct.
Higher than 99% of the other 919 observations since Jan 19504
CK forecast · Aug 2028
−0.15
80% range −1.07–0.895
  1. 1Latest observation against the observation one year earlier (for weekly data, the nearest within three days).
  2. 2Latest observation against the observation five and ten years earlier.
  3. 3Highest and lowest published observations across the full history shown.
  4. 4Share of the other published observations that are lower than the latest one, rounded down.
  5. 5Final period of the CK forecast, a statistical projection from the model in the methodology, with its 80% range; rounded to three significant figures.

Methodology

Each value is CPC's ONI: the three-month running mean of monthly sea surface temperature (SST) anomalies in the Niño 3.4 region (5°N–5°S, 120°–170°W), from NOAA's Extended Reconstructed SST dataset, version 6 (ERSST.v6). Anomalies are measured against centered 30-year base periods that CPC updates every five years, so long-term ocean warming is largely removed from the index. Each overlapping three-month season is plotted at its center month: December–February 1950 appears as January 1950, and November 1950–January 1951 appears as December 1950. Values are kept at the two-decimal precision of CPC's text file. CPC's historical convention classifies an El Niño episode when the ONI is at or above +0.5 °C, and a La Niña episode when it is at or below −0.5 °C, for at least five consecutive overlapping seasons. Since 1 February 2026 CPC uses the closely related Relative Oceanic Niño Index (RONI), which subtracts the tropical-mean SST anomaly, for official ENSO monitoring and alerts; CPC continues to update this legacy ONI for continuity, and the two can differ by several tenths of a degree. El Niño and La Niña matter for Southern California because they shift the Pacific storm track and coastal ocean conditions: strong El Niño winters have tended to bring wetter weather, larger winter swells and coastal flooding, temporarily higher sea levels and warmer coastal water that affects fisheries, while La Niña winters tend to be drier. Effects vary from event to event. We verified the series against CPC's published ONI table (ERSST.v6), which matched at one-decimal rounding for all 920 seasons, including the latest July–September 2026 value of about 2.2 °C. CPC notes the most recent values are estimates that may be revised for up to two months, and the full history can shift when base periods or the underlying SST dataset are updated. Projection: CK Economics statistical projection. The central path comes from an autoregression of order 6 (chosen by AIC) with a constant, so the central path returns toward the long-run average within months. It runs only as far ahead as backtests support: the model is refitted at past dates, its forecasts are scored against what happened, and it is shown only for horizons where its errors were at least 5% smaller than those of the better of a no-change forecast and repeating the same month a year earlier. The shaded band is the 80% range of those backtest errors. It is a conditional estimate that extrapolates past patterns: it does not model policy, tariffs, recessions or other shocks, and it is not an official forecast of the source agency.

How we collect, check and project every dataset →

Source

NOAA National Weather Service, Climate Prediction Center, Oceanic Niño Index (ONI, ERSST.v6): https://www.cpc.ncep.noaa.gov/data/indices/oni.ascii.txt — figures as published on 10 October 2026.

The 24 projected periods are a CK forecast, not figures from the source; the methodology above describes how they are made.

All data

920 observations, newest first · °C anomaly

Downloading means you accept our TermsCSVJSON
PeriodValueChange y/y
Aug 20262.16+2.42 °C
Jul 20261.8+1.91 °C
Jun 20261.39+1.41 °C
May 20260.95+0.99 °C
Apr 20260.46+0.44 °C
Mar 20260.11+0.19 °C
Feb 2026−0.21+0.01 °C
Jan 2026−0.39+0.07 °C
Dec 2025−0.6−0.17 °C
Nov 2025−0.61−0.32 °C
Oct 2025−0.57−0.38 °C
Sep 2025−0.43−0.31 °C
Aug 2025−0.26−0.22 °C
Jul 2025−0.11−0.17 °C
Jun 2025−0.02−0.2 °C
May 2025−0.04−0.47 °C
Apr 20250.02−0.75 °C
Mar 2025−0.08−1.26 °C
Feb 2025−0.22−1.75 °C
Jan 2025−0.46−2.3 °C
Dec 2024−0.43−2.42 °C
Nov 2024−0.29−2.19 °C
Oct 2024−0.19−1.93 °C
Sep 2024−0.12−1.62 °C