El Niño in India: What IMD’s September 2026 Update Actually Tells Us

El Niño is often reduced to one sentence: less rain in India. That is a useful warning, but a poor conclusion.

At the 23 September 2026 India-time cut-off, the latest India Meteorological Department (IMD) update reports strong El Niño conditions over the equatorial Pacific. The bulletin records a Niño 3.4 sea-surface-temperature anomaly of about +2.08°C for August 2026, measured against the 1991–2020 average. That number describes an unusually warm Pacific region; it is not an Indian rainfall total or a district-level weather forecast.

The more useful question is not simply whether El Niño is present. It is how much weight India should give it when interpreting the monsoon.

What does the September 2026 signal actually measure?

IMD describes El Niño as the warm phase of the El Niño–Southern Oscillation, or ENSO, involving unusual warming of sea-surface waters in the eastern tropical Pacific. Niño 3.4 is one monitored Pacific region used to describe that state. The +2.08°C figure is therefore an anomaly: the difference from the reference average, not the actual temperature of the ocean.

The sequence reported by IMD is important. La Niña conditions persisted from September 2025 through February 2026. ENSO became neutral in March, El Niño crossed its threshold in May, and the Niño 3.4 anomaly had strengthened to approximately +2.08°C by August. IMD’s coupled forecast system indicated that strong to very strong El Niño conditions were likely to persist and strengthen through the end of 2026.

The same bulletin gives an important part of the Indian context: the Indian Ocean Dipole, or IOD, was neutral in July–August 2026, and neutral conditions had the highest probability through the forecast period. That does not turn the IOD into a simple counterweight to El Niño. It shows why an India-focused reading should not treat one Pacific index as the whole climate story.

Does a strong El Niño guarantee a weak Indian monsoon?

No. It raises concern, but it does not determine the result on its own.

IMD’s historical El Niño page lists 17 events from 1951 to 2023 alongside the seasonal southwest monsoon rainfall departure. Twelve of those entries have negative departures, while five have positive departures. The pattern supports a general association between El Niño and below-normal Indian monsoon rainfall, but it also contains clear exceptions.

For example, the table records a negative departure of 22.3% in the moderate El Niño year 1972 and 20.9% in the weak El Niño year 2002. But the strong El Niño year 1997 had a departure of +0.2%, which was close to normal. Weak El Niño years also include positive departures: +10.7% in 1953 and +13.9% in 1994.

That comparison changes how the headline should be read. The strength label describes the Pacific anomaly, not a fixed percentage for India. A stronger Pacific signal does not automatically translate into a proportionally weaker all-India monsoon. The historical record gives El Niño value as a risk indicator, not as a complete prediction.

It also explains why a national seasonal signal cannot answer every local question. An all-India seasonal departure does not say whether a particular state will receive normal rainfall, whether rainfall will be evenly distributed, or whether a short spell will be wet or dry. Those are different questions with different time and geographic scales.

What did IMD forecast for 2026, and what is still unconfirmed?

In its second-stage forecast issued on 29 May 2026, IMD estimated June–September rainfall at 90% of the Long Period Average, with a model error of ±4%. The LPA used for that forecast was approximately 87 cm, based on the 1971–2020 period. IMD classified the outlook as below normal.

The release also assigned probabilities to rainfall categories: 60% for deficient rainfall, 24% for below-normal rainfall, 14% for normal rainfall, 2% for above-normal rainfall and 0% for excess rainfall.

These figures are easy to misread. The 90% is the forecast amount relative to the LPA; it is not a 90% probability. The probability figures describe the likelihood of separate rainfall categories. Keeping those two kinds of number apart prevents a forecast estimate from being mistaken for a certainty.

The May release was a forecast made while ENSO conditions were transitioning from neutral towards El Niño. The September bulletin is a later update on the Pacific and Indian Ocean state. Neither should be presented as the final measured result for India’s 2026 monsoon.

At the stated cut-off, IMD’s monsoon activity page did not list a completed 2026 end-of-season report. That means the May estimate should remain labelled as a forecast, rather than being rewritten as the season’s observed national rainfall. For current Indian conditions, IMD’s rainfall-information pages provide daily, weekly, monthly and cumulative views, including state, district and meteorological-subdivision perspectives.

How should an India-focused reader use the El Niño headline?

A disciplined reading has three layers.

First, use the ENSO–IOD bulletin to understand the large-scale background: the Pacific is in a strong El Niño phase, while the IOD is currently described as neutral. This tells us that the climate signal deserves attention, but it does not provide a rainfall figure for India.

Second, keep forecasts separate from observations. The 90% of LPA figure belongs to IMD’s 29 May seasonal forecast for June–September. It should not be mixed with the August Niño 3.4 observation or treated as a live local forecast. The dates, variables and geographic areas are different.

Third, match the question to the right Indian evidence. A reader asking whether the country’s monsoon matched the forecast needs the eventual seasonal assessment. A reader asking about current conditions in a state or district needs the relevant observed-rainfall view. A reader asking why the monsoon risk was elevated needs the ENSO history and the current Pacific–Indian Ocean update.

This separation is more informative than simply repeating that El Niño is bad for India. It shows what is known, what is being forecast and what still has to be measured.

The defensible answer in September 2026

El Niño matters for India because IMD’s historical record shows that it is generally associated with a weaker southwest monsoon. The current event is not a minor signal: IMD reports a strong Pacific anomaly and expects strong to very strong conditions to continue through the end of 2026.

But strong El Niño does not prove that India’s rainfall will be deficient everywhere, nor does it settle the final 2026 monsoon outcome. The historical exceptions, the neutral IOD assessment and the absence of a completed 2026 end-of-season report all point to the same conclusion: El Niño is a serious background risk, not a monsoon verdict.

The right headline is therefore narrower and more useful: India has a strong El Niño signal to account for, but the country’s actual monsoon outcome must be judged from Indian rainfall observations and the completed seasonal assessment—not from the Pacific index alone.