The El Niño Briefing #5: The raw index just set a record for a June–August. The corrected one says +1.4

NOAA posted the June–August reading of its headline index this morning, and it is the highest June–August in the record.

The Oceanic Niño Index for JJA 2026 came in at +1.80 °C. No June–August since 1950 has been that warm — 1997 was +1.48, 2015 was +1.44. It also carries the event past +1.5, the line the agency uses for "strong", for the first time on a three-month mean rather than a weekly reading.

That is the raw number. Here is the corrected one.

On the same table, the relative index — RONI, which subtracts the warming of the whole tropical ocean so that 2026 can be compared with 1982 on equal terms — reads +1.4 for June–August. That is up from +1.0 in May–July and +0.5 in April–June: about half a degree a season, and not slowing. Under RONI the three benchmark events peaked at +2.4 (1982–83), +2.3 (1997–98) and +2.3 (2015–16). At +1.4 this event is still below all three. The gap is closing at the rate you would expect from an event with a September–December peak ahead of it, and no faster.

So the honest sentence is the same as last week's, with the numbers moved up: the raw index is in record territory for the calendar date, and the corrected index says "strong, rising, not yet historic".

The weekly reading held. Niño 3.4 for the week centred 26 August is +2.6 °C — the third week at 2.6–2.7. Flat is not a turn; the next weekly update lands Monday.

A correction of ours. Last Tuesday the site's 2026 page took the forecast centre's "69% chance of a historic event — +2.5 °C or more in October–December" and compared it with the ONI record. That threshold is on RONI, not ONI; CPC says so in the same sentence, and we read past it. Fixed on Wednesday. The corrected comparison is starker, not softer: +2.5 on RONI in a single autumn would exceed every three-month value in the relative index since 1950, where the record is +2.4 (November–January, 1982–83). Same lesson as the race chart two weeks ago — two rulers, one line, and the error always flatters the headline.

What it is already doing — three items, each from the primary source.

• Panama Canal. The Canal Authority's Advisory A-29-2026 caps transits at 34 a day from today, falling to 32 from 15 September. Its reason, in its own words: rainfall across the watershed since May is 34% below the historical average and inflows 44% below, with the coming El Niño expected to make it worse.
• Indonesia. NASA's Earth Observatory on Wednesday, on the peatland fires darkening skies over Sumatra and Borneo: "The strong El Niño is making the dry season drier over the fire-prone parts of the country and exacerbating burning — just as we anticipated it would." The two worst fire years in recent decades were 1997 and 2015.
• Atacama. Widespread snow across the driest desert on Earth, 27 August. Climatologist René Garreaud, quoted by NASA, called the strengthening El Niño "the backdrop" for an anomalously wet winter in north-central Chile — the subtropical high that keeps the region dry weakens during these events.

The outlook is unchanged until the next official discussion on 10 September: peak still October–December, better than 90% odds of a very strong event, 69% odds of the +2.5 RONI reading described above.

One question, and a one-line reply is enough. You are one of about fifty people who open this every week, and a few of you work somewhere this number matters — a port, a ministry, a trading desk, a food agency. What decision does this reading feed for you, or what is missing from it that you need? Reply to this email; I read every one.

Live dashboard — ONI and RONI now show the June–August rows →