ENSO Tracker

Updated 2026-07-20 · Sources: NOAA/CPC & IRI

Current State The Niño-3.4 region (5°N–5°S, 170°W–120°W) SST anomaly is the primary ENSO index. Values above +0.5 °C indicate El Niño; below −0.5 °C indicate La Niña. This weekly reading comes from NOAA/CPC's Reynolds OI SST file (wksst9120.for), using a 1991–2020 climatological base period.

El Niño Advisory
+2.10 °C
Super El Niño
Niño-3.4 SST anomaly (weekly)

Anomaly Gauge Visual indicator of ENSO phase and intensity. The needle maps the current Niño-3.4 anomaly to ±0.5 °C (weak), ±1.0 °C (moderate), ±1.5 °C (strong), and ±2.0 °C (very strong) thresholds. ONI and RONI below are 3-month running means.

La NiñaNeutralEl Niño
ONI 0.98 (AMJ 2026)
RONI 1.5 (Jun 2026)

CPC Advisory The official NOAA/CPC ENSO Diagnostic Discussion, issued monthly. An El Niño or La Niña Advisory is declared when the Oceanic Niño Index (ONI) meets or exceeds ±0.5 °C for five consecutive overlapping 3-month seasons.

El Niño continues and will strengthen through the end of the year, with a 97% chance it will persist through early spring 2027.

Niño-3.4 Weekly Anomaly — Last 52 Weeks Weekly Niño-3.4 SST anomaly over the past 52 weeks, from NOAA/CPC's Reynolds OI SST file (wksst9120.for, base period 1991–2020). Dashed lines at ±0.5 °C mark the boundary between ENSO phases.

El Niño (≥ +0.5 °C) Neutral La Niña (≤ −0.5 °C)

ONI vs RONI — Last 3 Years (Monthly) ONI (Oceanic Niño Index) is the standard 3-month running mean of the Niño-3.4 anomaly — the primary metric NOAA uses to classify El Niño and La Niña events. RONI (Relative ONI) applies a linear detrending to remove the long-term warming signal.

Regional Impacts — Super El Niño Typical regional climate impacts associated with the current ENSO phase, based on historical composites from NOAA/CPC. Actual impacts vary by location, season, and event intensity.

IRI / CPC Forecast Figures

CPC ENSO Probability Forecast

Figure 1 — CPC ENSO Probability Forecast CPC's probabilistic forecast showing the likelihood of El Niño, Neutral, and La Niña conditions for each upcoming season, based on a consolidation of dynamical and statistical model guidance.

IRI Historical SST Anomaly

Figure 2 — Niño-3.4 Historical SST Anomaly Historical time series of observed Niño-3.4 SST anomalies, providing context for how the current state compares with recent years.

IRI ENSO Probability Forecast

Figure 3 — IRI ENSO Probability Forecast IRI's probabilistic ENSO forecast, blending output from multiple dynamical models, statistical models, and expert judgment. Issued mid-month.

Figure 4 — IRI SST Model Forecast Plume (Niño-3.4 Anomaly) Each line is one model's Niño-3.4 anomaly forecast. ● Filled circles = dynamical models: physics-based coupled ocean–atmosphere GCMs that simulate the fluid equations governing climate (e.g. ECMWF, NCEP CFSv2). ○ Open circles = statistical models: data-driven methods trained on historical SST patterns (e.g. CPC CA, LDEO). ◇ Open diamonds = relative models: forecast the Niño-3.4 anomaly expressed relative to the tropical Pacific mean SST rather than a fixed climatological baseline, removing the long-term warming trend (the same concept as RONI). Stars = ensemble averages per type. Use the dropdown to filter.

Individual model forecasts coloured by model — hover any line to see its name and value. Ensemble averages and observed (dashed blue) are labelled in the legend.

ENSO Strength Categories Stacked bar chart showing the percentage of IRI models predicting each ENSO strength category (Very Strong La Niña through Very Strong El Niño) for each upcoming season. Numbers inside bars show the model count. Taller red bars indicate stronger El Niño consensus.

Percentage of IRI models predicting each ENSO strength category per season. Numbers inside bars show model count. Hover for details.