RONI is still at –0.1°C. El Niño is officially here. Both statements are true — and understanding why is the key to reading the next three months of data correctly.
On June 11, 2026, NOAA's Climate Prediction Center issued an El Niño Advisory. The language was unambiguous: "El Niño conditions are present and expected to strengthen into the Northern Hemisphere winter 2026–27." If you had then pulled up the official RONI seasonal table — the very index NOAA switched to in February 2026 as its primary El Niño metric — you would have found a value of –0.1°C for March–May 2026.
Negative. Below zero. Below the +0.5°C threshold that officially defines El Niño.
Both numbers are accurate. Neither is wrong. But together they expose something important about how El Niño is measured — and why fluent readers of NOAA data need to understand the lag built into the system before the July 9 CPC Diagnostic Discussion arrives.
RONI — the Relative Oceanic Niño Index — is a three-month running average of sea surface temperature anomalies in the Niño 3.4 region, expressed relative to a shifting 30-year baseline rather than an absolute climatology. That relative framing matters enormously right now, because the entire global tropics are running roughly +1°C above historical norms. By measuring against a recent baseline, RONI strips out that background warmth and isolates only the El Niño signal itself.
The three-month average is the source of the lag. When NOAA published the MAM (March–April–May) RONI value of –0.1°C in mid-June, it was averaging data that included March — a month when the Pacific was still transitioning. The signal from April and May, both warmer, gets diluted by the earlier, cooler month. The index is always looking backward.
The RONI seasonal sequence tells a clear directional story: –0.9°C (DJF), –0.7°C (JFM), –0.4°C (FMA), –0.1°C (MAM). Each three-month window has warmed by 0.3°C relative to the last. At that pace, the April–May–June (AMJ) value — which CPC will publish on July 9 — is projected to cross +0.5°C for the first time in this cycle. That is the moment the official seasonal index formally enters El Niño territory.
While the seasonal index was still catching up, the weekly Niño index readings — which CPC also publishes and which the advisory actually rests on — had already crossed into El Niño range. As of June 11, CPC's weekly relative Niño 3.4 was at +0.7°C, with Niño 3 at +1.0°C and Niño 1+2 — the far eastern Pacific — at a striking +2.1°C. By the week ending June 14, BOM's relative Niño 3.4 had risen further to +0.92°C — above BOM's own +0.80°C El Niño threshold.
| Index | Region | Week of June 11 (CPC) | NOAA warm threshold |
|---|---|---|---|
| Niño 1+2 | Far eastern Pacific | +2.1°C | +0.5°C |
| Niño 3 | East-central Pacific | +1.0°C | +0.5°C |
| Niño 3.4 (RONI basis) | Central Pacific benchmark | +0.7°C | +0.5°C (NOAA) / +0.8°C (BOM) |
| Niño 4 | West-central Pacific | +0.7°C | +0.5°C |
The weekly indices had moved into warm territory across all four regions, with the central Pacific signal at or above El Niño thresholds depending on agency and framework — NOAA uses +0.5°C for its weekly relative readings; BOM's threshold for sustained monthly values is +0.8°C, which its own relative Niño 3.4 had crossed by June 14.
"The advisory rests on the weekly data and the atmospheric response — not on the seasonal index that defines El Niño in the record books."
The atmospheric side of the ledger confirms it too. CPC's June 11 discussion documented low-level westerly wind anomalies across the central equatorial Pacific, suppressed convection near Indonesia, and a weakened Walker Circulation — all canonical El Niño atmospheric signatures. ENSO is fundamentally a coupled ocean-atmosphere phenomenon. When the ocean and the atmosphere are both responding, the advisory is justified even when the seasonal averaging index hasn't formally crossed.
There's a second number worth flagging. If you've read IRI's June Quick Look, you may have seen Niño 3.4 cited as +1.7°C — not +0.9°C. That is not a discrepancy. It is the difference between two legitimate measurement frameworks.
CPC and BOM now report relative SST anomalies — measured against a shifting 30-year baseline that moves with the warming trend. IRI reports the traditional absolute anomaly, measured against a fixed 1991–2020 climatology. The global tropics are running roughly +1°C above that older baseline, so IRI's figure is approximately 1°C higher than CPC's for the same week. Neither is wrong. They are answering different questions: IRI's absolute value captures total warmth in the Pacific; CPC's relative value isolates how much of that warmth is specifically El Niño, above and beyond background ocean warming.
For tracking El Niño strength and comparing to historical events — which were measured using the older absolute climatology — the absolute figure is actually more useful. The 1997–98 peak of +2.3°C and the 2015–16 peak of +2.6°C were both measured in absolute terms. When analysts project this event to rival or exceed those peaks, they are generally referencing absolute anomalies. By that measure, the current weekly reading near +1.7°C is already a moderate El Niño and climbing.
The next CPC ENSO Diagnostic Discussion is scheduled for July 9, 2026. It will be the first to publish an AMJ RONI value — and based on the trajectory, AMJ is the most likely first seasonal crossing above +0.5°C. If that happens, the official seasonal record will formally confirm what the weekly data and the advisory have already established.
July 9 will also update the strength probability — currently at 63% for a "very strong" event (Niño 3.4 ≥ +2.0°C) during November–January. Watch for whether that odds figure moves upward as the spring predictability barrier recedes further into the past and model ensembles tighten.
Between now and July 9, NOAA publishes weekly SST updates every Monday. Watch the relative Niño 3.4 figure: if it holds above +0.9°C and continues toward +1.2°C, the AMJ seasonal average will comfortably cross the threshold. If it stalls or retreats — which would require a meaningful reversal of the current westerly wind pattern and subsurface heat — the July 9 discussion will be more cautious.
The Niño 1+2 figure is the leading edge. At +2.1°C, it is already at the level that, in analogous east-based events like 1982–83, preceded rapid intensification of the central Pacific signal. That east-based fingerprint — which we covered on June 23 — remains the most informative single data point in the current dataset.
The scoreboard will catch up to the game by July 9. The game itself is already well underway.
NOAA CPC ENSO Diagnostic Discussion, June 11, 2026 · CPC ENSO Evolution PDF, June 15, 2026 · IRI ENSO Quick Look, June 2026 · BOM ENSO Wrap-Up, June 14, 2026