El Niño 2026: What NOAA's RONI Says and How the Predictions Settle

NOAA's Climate Prediction Center (CPC) said on 8 October 2026 that El Niño is still strengthening, with a strong to very strong event, a RONI of +1.5°C or more, likely through January to March 2027, a chance it puts above 83%. On versus at 04:10 UK time on 9 October 2026, Yes on Will El Niño reach super strength? was priced at 97.2p and Yes on Will this El Niño set a new strength record? at 83p.

Both predictions turn on one number, the Relative Oceanic Niño Index, or RONI. This guide covers what RONI measures, where the numbers stand after the CPC's October update, how both predictions settle and what a position can cost you.

The Short Answer

• El Niño is under way. The CPC kept its El Niño Advisory in force on 8 October 2026 and says El Niño continues to strengthen.
• The number to watch is RONI. Its latest published value, for July to September, is +1.69°C, and the CPC's middle forecast for September to November is +2.47°C.
• Two predictions, two lines. One asks whether RONI reaches +2.0°C. The other asks whether it goes above +2.40°C, the highest value in the CPC's record, which starts in 1950.

What RONI Measures

El Niño is a spell of unusually warm surface water in the central and eastern tropical Pacific. In February 2026 the CPC adopted RONI in place of the older Oceanic Niño Index. RONI compares the main El Niño region with the tropical oceans as a whole, so it depends less on a 30-year average that struggles to keep pace with changes in tropical temperatures.

Each RONI value is a three-month average named by the first letters of its months: ASO is August, September and October, and NDJ is November, December and January. The index measures ocean temperature, not the weather where you live, and the CPC notes that a stronger event makes El Niño impacts more likely but not certain.

Where the Numbers Stand

These figures come from the CPC's ENSO diagnostic discussion of 8 October 2026, its October RONI outlook and strength probabilities, its RONI table and its RONI data file, checked on 9 October 2026.

• Latest reading: +1.69°C for July to September, up from +1.36°C for June to August, in the CPC's data file (its web table rounds them to 1.7 and 1.4). The CPC says the newest values are estimates that can change for up to two months.
• The discussion: last month sea surface temperatures were more than +4.0°C above average in parts of the eastern equatorial Pacific, and the CPC's one-month Niño-3.4 reading was +2.1°C. RONI is a three-month average of that kind of reading, so the two are not the same number, and neither prediction uses the monthly one.
• Very strong odds: the CPC puts the chance of a reading at or above +2.0°C, which it calls very strong, at 100% for September to November and for October to December, 96% for November to January, 81% for December to February and 46% for January to March.
• A historic event: the CPC puts the chance of a three-month RONI of +2.5°C or more, which would beat every El Niño since 1950, at 54% for September to November, 83% for October to December and 70% for November to January. That bar is higher than the +2.40°C line in the record prediction.
• The middle forecast: the CPC's 50% line is +2.47°C for September to November, +2.74°C for October to December, +2.65°C for November to January and +2.36°C for December to February.

The highest value in the CPC's data so far is +2.40°C, for December 1982 to February 1983. The CPC's October tables begin with September to November, so they give no forecast for August to October, the first of the five seasons the predictions count. Its middle forecasts for September to November, October to December and November to January sit above the record line, and the one for December to February just under it. These are forecasts, not results, and a forecast is not a price.

What the Two Predictions Ask

Each prediction has two answers, Yes and No, priced between 0p and 100p. Both use the CPC's published RONI values for five seasons: August to October, September to November, October to December, November to January and December to February, running from late 2026 into early 2027. They are about that number, not about rainfall, storms or temperatures in any place, and they use RONI, not the older Oceanic Niño Index, so figures quoted elsewhere may not match.

• "Will El Niño reach super strength?" Yes if any of the five values is +2.0°C or higher. "Super" is the prediction's label: the CPC's own word for that band is "very strong". Yes can settle as soon as a qualifying value appears. If none has qualified, No waits for the December to February value, because the rules treat that season as the usual peak.
• "Will this El Niño set a new strength record?" Yes if any of the five values is above +2.40°C, the December 1982 to February 1983 figure. Equalling it is not enough.

How These Predictions Settle

Every market names the source that settles it before you trade (what market resolution means explains the idea). Here it is the RONI values the CPC publishes. If the condition is met, Yes settles at 100p and No at 0p; if not, the reverse. Two rules matter most:

1. The first published value for a season is final. The CPC warns that recent values can change, but under the rules no later revision alters the result once a season's first value is out.
2. Precision matters at the edge. The CPC's web table rounds to one decimal place, while its data file gives two, and the super strength rules point to the web page. Check a value that lands close to +2.0°C or +2.40°C against both. For the record prediction, equalling +2.40°C does not count.

A Worked Example

Say Yes on the super strength prediction trades at 90p, a made-up price for illustration. You put 900p into Yes, which buys 10 contracts, and the 2% transaction fee adds 18p, so 918p leaves your balance. If the CPC publishes a qualifying value, the contracts settle at 100p each, 1,000p in total, 82p more than you paid. If no season qualifies, they settle at 0p and the 918p is gone. At a high price the possible gain is small next to the possible loss, and a forecast of 90% or more is still not a certainty. There is no leverage and no margin call, so the most this position could cost you was the 918p you saw before confirming.

The Next Dates

• By 5 November 2026: the CPC says it updates its RONI table by the 5th of each month, so the August to October value should appear. A value of +2.0°C or higher may settle the super strength prediction Yes at once, and one above +2.40°C may do the same for the record prediction. A lower value settles neither: later seasons can still qualify.
• 12 November 2026: the CPC's next monthly discussion and outlook. It settles neither prediction, but it brings new chances.
• December 2026 to March 2027: each later season follows a month after the one before it, so on the CPC's schedule September to November is due by early December and December to February by early March 2027. If no season has reached +2.0°C, the super strength prediction cannot settle No before that last value is out.
• 1 April 2027: the listed end of both predictions (when markets close explains deadlines).

Before you trade

You can lose the whole amount you put into a position: a prediction that settles against your answer pays 0p, and a price is only the market's estimate at a given moment, not a promise. versus is licensed by the UK Gambling Commission under account 101143, which you can check on the Commission's public register. A 2% transaction fee is added on top of the stake and shown before you confirm. Safer Play tools include deposit limits, loss limits, reality checks, time out and self exclusion, alongside GAMSTOP; the safer play page explains each one, and how it works follows one position from opening to settlement. Only put in what you are comfortable losing.

Frequently asked questions

Is El Niño happening in 2026?

Yes, according to NOAA's Climate Prediction Center, which kept its El Niño Advisory in force in its discussion of 8 October 2026 and says El Niño continues to strengthen.

What is RONI?

The Relative Oceanic Niño Index, a three-month average of ocean temperature in the main El Niño region compared with the tropical oceans as a whole. The CPC adopted it in February 2026.

When is the next RONI value due?

By 5 November 2026, when the CPC says it updates its RONI table. It should add August to October. The CPC's next monthly discussion is scheduled for 12 November 2026.

What counts as a super El Niño on the versus prediction?

A RONI value of +2.0°C or higher, as first published by the CPC, for any of five seasons: August to October, September to November, October to December, November to January or December to February, from 2026 into early 2027.

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