Each panel tracks the sea surface temperature of one patch of the equatorial Pacific over the past twelve months. The line shows how far the water there sits above or below normal for the time of year, in degrees Celsius. The panels run west to east, top to bottom.
The four regions
- Niño 4:
- Central Pacific around the date line (5°N–5°S, 160°E–150°W).
- Niño 3.4:
- Straddles the central and eastern Pacific (5°N–5°S, 170°W–120°W). The region NOAA uses to declare El Niño and La Niña — the one to watch.
- Niño 3:
- Eastern Pacific (5°N–5°S, 150°W–90°W).
- Niño 1+2:
- A small box off the coasts of Peru and Ecuador (0–10°S, 90°W–80°W). Often the first to warm and the most volatile.
How to read it
- Orange, above the zero line, is warmer than normal. Blue, below it, is cooler.
- Start with Niño 3.4. Readings of +0.5 °C or more point to El Niño conditions, −0.5 °C or less to La Niña. The further from zero, the stronger the event.
- Look at the trend over weeks and months rather than any single week. NOAA only classifies an El Niño or La Niña episode once the departure has persisted across several overlapping three-month seasons.
- Each panel has its own vertical scale, so compare the numbers on the axis, not the heights of the shading. Niño 1+2 swings far more than Niño 4.
- Warming that starts off South America (Niño 1+2) and spreads west is a classic El Niño pattern; warmth concentrated in the central Pacific (Niño 4) with the east near normal is the “Modoki” or central-Pacific type.
Why the numbers differ from the status panel
This chart shows relativeanomalies: each region’s departure with the average warming of the whole tropical ocean subtracted. That strips out the background warming of the oceans so the El Niño signal itself stands out, and it means the Niño 3.4 line here usually sits below the traditional weekly anomaly quoted in the status panel above. Both come from NOAA’s Climate Prediction Center; NOAA’s official episode classification uses the traditional Oceanic Niño Index.
