Explained: Why even a strong El Niño does not guarantee a poor Indian monsoon
In one line: El Niño usually weakens India's monsoon, but the Indian Ocean Dipole, the location of Pacific warming and intraseasonal waves can soften or deepen its effect, as the contrast between 1997 and 2026 shows.
Published 2 November 2026. Written by Pratidin from the reports linked at the end; every fact checked by a separate review before publishing. How we work
India's 2026 southwest monsoon ended with 759.4 mm of rain against a normal of 868.6 mm, 12.6% below normal and the weakest season since 2015, during a strong El Niño. A Hindu explainer on 2 November 2026 asks why El Niño, the periodic warming of the central and eastern equatorial Pacific, does not always produce a poor monsoon. It counts seven Indian monsoons since 1950 that coincided with a moderate or strong El Niño. Five of them, including 2026, were deficient (at least 10% below the long-period average), 2023 was below normal, and 1997 was normal.
The main offsetting factor is the Indian Ocean Dipole (IOD), the difference in sea surface temperature between the western Indian Ocean near Africa and the eastern Indian Ocean near Indonesia. A positive IOD, with a warmer west, helps draw moisture to India. In 1997 a strong positive IOD partly neutralised one of the strongest El Niño events on record, and the warmest Pacific water lay farther east, near South America. In 2015 the IOD barely developed, which the explainer links to a shift in the westerly wind belt around Antarctica. The Madden-Julian Oscillation, a band of cloud and rain that circles the tropics every 30 to 60 days, also matters: in August 2023 it stayed away from India, which had its driest August since 1901.
The explainer notes that the IMD updates its April monsoon forecast at the end of May and has combined several global climate models since 2021. Its forecasts come with an error margin, and in 2026 the IOD stayed neutral, as IMD's model had expected, while some other models had predicted a positive IOD. The stakes are high: the monsoon brings about three-quarters of India's annual rainfall and about 40% of farmland is unirrigated. The lesson, the explainer argues, is that El Niño raises the risk of a poor monsoon but does not decide it on its own.
Prelims facts
- The 2026 monsoon ended 12.6% below normal (759.4 mm against 868.6 mm), the weakest since 2015.
- Of seven moderate or strong El Niño monsoons since 1950, five were deficient; 2023 was below normal and 1997 normal.
- A positive Indian Ocean Dipole (warmer western Indian Ocean) can offset El Niño, as in 1997.
- The Madden-Julian Oscillation circles the tropics every 30 to 60 days; August 2023 was India's driest August since 1901.
- IMD has used a multi-model ensemble for monsoon forecasts since 2021.
Quick recall
- 2026 monsoon rainfall against normal?
- 759.4 mm against 868.6 mm, 12.6% below normal, the weakest since 2015.
- What is a deficient monsoon?
- Seasonal rainfall at least 10% below the long-period average.
- Moderate or strong El Niño monsoons since 1950 counted in the explainer, and how many were deficient?
- Seven; five were deficient.
- Which strong El Niño year had a normal Indian monsoon, and why?
- 1997, helped by a strong positive Indian Ocean Dipole.
- What is a positive Indian Ocean Dipole?
- Western Indian Ocean warmer than the eastern Indian Ocean near Indonesia.
- Period of the Madden-Julian Oscillation?
- About 30 to 60 days, moving eastward around the tropics.
- Driest August in India since 1901?
- August 2023.
- Since when has IMD used a multi-model approach for monsoon forecasts?
- 2021.
Prelims practice question
With reference to the Indian monsoon, consider the following statements:
1. A positive Indian Ocean Dipole is associated with a warmer western Indian Ocean relative to the eastern Indian Ocean.
2. Every moderate or strong El Niño year since 1950 has produced a deficient Indian monsoon.
3. The Madden-Julian Oscillation is an eastward-moving disturbance that circles the tropics in about 30 to 60 days.
Which of the statements given above are correct?
- 1 and 2 only
- 2 and 3 only
- 1 and 3 only
- 1, 2 and 3
Show answer
Answer: (c) 1 and 3 only. Statement 1 is correct. Statement 2 is wrong: of seven such years, 1997 was normal and 2023 below normal but not deficient. Statement 3 is correct.
Use this in UPSC Mains: previous-year questions
Recurring theme: Monsoon variability and its ocean-atmosphere drivers
- How to use this
Argue that El Niño is a major but not sole driver, using the IOD, MJO and the record of El Niño monsoons since 1950.
- Of seven moderate or strong El Niño monsoons since 1950, five were deficient, but 1997 was normal and 2023 only below normal.
- In 1997 a strong positive Indian Ocean Dipole offset one of the strongest El Niño events on record.
- The Madden-Julian Oscillation kept rain away in August 2023, India's driest August since 1901.
The question concerns preparedness for El Niño fallouts under NDMA's 2010 drought guidelines, which the story does not cover.
The explainer states that the IOD compares the western and eastern Indian Ocean (not the Pacific) and can offset El Niño's impact on the monsoon, so the answer is (b) 2 only.
Mains practice question
"El Niño raises the risk of a poor Indian monsoon but does not decide it." Examine this statement with reference to the Indian Ocean Dipole and other factors. (250 words)
Model answer
El Niño, the warming of the central and eastern equatorial Pacific, usually suppresses India's monsoon, yet its effect varies from year to year.
Why El Niño raises the risk
- It shifts the Walker circulation, bringing dry, sinking air over India.
- Of seven moderate or strong El Niño monsoons since 1950, five were deficient, including 2026 (12.6% below normal).
Why it does not decide
- Indian Ocean Dipole: a positive IOD draws moisture to India; in 1997 it partly cancelled a very strong El Niño and the monsoon was normal.
- Location of warming: in 1997 the warmest water lay far east near South America; central Pacific warming hurts India more.
- Madden-Julian Oscillation: its 30 to 60 day cycle can cause long breaks; August 2023 was the driest since 1901.
- Remote drivers: a shift in Antarctic westerlies is linked to the weak IOD of 2015.
Implications
- Forecasts need multi-model ensembles, as IMD has used since 2021.
- Contingency crop plans, water storage and food stocks should respond to risk, not certainty.
- The monsoon brings about three-quarters of annual rainfall and about 40% of farmland is unirrigated, so even a probable shortfall demands early action.
- Better observation of the Indian Ocean would improve IOD forecasts, a known weak spot.
El Niño is a strong signal, but India's monsoon is shaped by an interplay of Pacific, Indian Ocean and atmospheric factors.
The basics
Why this matters
The 2026 monsoon ended 12.6% below normal during a strong El Niño. Yet in 1997, during one of the strongest El Niño events on record, India's monsoon was close to normal. A Hindu explainer on 2 November 2026 asks why. The answer, that several ocean and atmospheric systems interact, is classic GS1 geography and a frequent Prelims theme.
What El Niño is
El Niño is the periodic warming of the central and eastern equatorial Pacific Ocean, linked to a weakening of the trade winds and a shift in the Walker circulation, the east-west loop of air over the Pacific. It is the warm phase of the El Niño-Southern Oscillation (ENSO). Over India it tends to bring sinking, dry air and a weaker monsoon.
- 1Warm water spreads east along the equatorial Pacific
- 2The zone of rising, rainy air moves east, away from the western Pacific
- 3The Walker circulation shifts so that dry air tends to sink over the Indian region
- 4Rainfall is suppressed, often by 10% or more
Not one factor but several
The explainer counts seven monsoons since 1950 that coincided with a moderate or strong El Niño. Five of them, including 2026, were deficient, at least 10% below the long-period average. 2023 was below normal, and 1997 was normal.
The Indian Ocean Dipole
The main offsetting factor is the Indian Ocean Dipole (IOD): the difference in sea surface temperature between the western Indian Ocean near Africa and the eastern Indian Ocean near Indonesia. In a positive IOD the west is warmer, which helps draw moisture towards India. In 1997 a strong positive IOD partly cancelled El Niño. In 2015 the IOD barely developed, and the explainer links this to a shift in the westerly wind belt around Antarctica.
- One of the strongest El Niño events on record
- Strong positive IOD
- Monsoon close to normal
- Strong El Niño
- IOD barely developed
- Deficient monsoon
Other players
Where in the Pacific the warmest water lies also matters: warming in the central Pacific is more likely to send dry, sinking air over India. The Madden-Julian Oscillation, a band of clouds and rain that circles the tropics every 30 to 60 days, can bring or withhold rain for weeks. In August 2023 it stayed away from India, and the month was the driest August since 1901. The IMD now combines several global models in its IMD monsoon forecasting, and its forecasts carry an error margin. Background: El Niño-Southern Oscillation.
Go deeper
Why it matters for UPSC
The monsoon brings about three-quarters of India's annual rainfall and about 40% of farmland is unirrigated, so its failure hits food, prices and rural incomes. Prelims tests ENSO, IOD and MJO; Mains asks whether El Niño explains all climatic anomalies.
The core idea
El Niño-Southern Oscillation sets the background: a warm Pacific tends to suppress monsoon rain. But the Indian Ocean Dipole can offset it when positive, as in 1997. The Madden-Julian Oscillation can add or remove rain for weeks within a season. Because so many factors interact, IMD monsoon forecasting now uses several models and gives forecasts with an error margin.
Numbers and dates to remember
- 2026 monsoon: 759.4 mm against a normal of 868.6 mm, 12.6% below normal, the weakest since 2015
- Seven moderate or strong El Niño monsoons since 1950; five deficient (including 2026), 2023 below normal, 1997 normal
- Deficient: rainfall at least 10% below the long-period average
- August 2023: driest August since 1901
- IMD has used a multi-model approach since 2021
Where to go next
- El Niño-Southern Oscillation: the Pacific cycle behind El Niño and La Niña
- Indian Ocean Dipole: the Indian Ocean's own see-saw that can offset El Niño
- Madden-Julian Oscillation: the travelling rain band that shapes weeks of a monsoon
- IMD monsoon forecasting: how India forecasts the season and why errors happen
Go deeper: Is El Niño destiny for the monsoon?
The case that it mostly is. Five of the seven monsoons since 1950 that coincided with a moderate or strong El Niño were deficient. In 2026, with a strong El Niño, rainfall was 759.4 mm against a normal of 868.6 mm, 12.6% below normal and the weakest season since 2015. Policymakers rightly treat an El Niño forecast as a warning for food stocks, contingency crop plans and water storage.
The case that it is not. 1997 had one of the strongest El Niño events on record, yet the monsoon was normal because a strong positive Indian Ocean Dipole drew moisture towards India and the warmest Pacific water lay far to the east, near South America. 2023 was below normal rather than deficient. So El Niño shifts the odds; it does not decide the outcome.
Within-season swings. The Madden-Julian Oscillation can produce long dry spells even in a near-normal year. In August 2023 it stayed over Africa and the Americas, and India had its driest August since 1901.
What this means for forecasts. Because the IOD and MJO are harder to predict months ahead than ENSO, seasonal forecasts carry a band of error. The IMD monsoon forecasting system now blends several global models, but an individual season can still land at the edge of the forecast range. For the bigger picture of Pacific variability, see El Niño-Southern Oscillation.
El Niño-Southern Oscillation
The Pacific cycle behind El Niño and La Niña
In one line: ENSO is a recurring cycle of ocean warming and cooling in the equatorial Pacific, coupled with swings in air pressure called the Southern Oscillation.
Three phases
- El Niño: the central and eastern Pacific is warmer than normal; trade winds weaken. It tends to weaken India's monsoon.
- La Niña: the same region is cooler than normal; trade winds strengthen. It tends to favour a good monsoon.
- Neutral: neither condition holds.
Events recur every two to seven years. Scientists track them through sea surface temperature in the Niño 3.4 region and through the pressure difference between Tahiti and Darwin.
Why it is in the news
A strong El Niño in 2026 coincided with a monsoon 12.6% below normal. The Hindu explainer shows that El Niño alone does not settle the outcome.
Where to go next
El Niño-Southern Oscillation: every story that connects to it (2)
Indian Ocean Dipole
The Indian Ocean's see-saw that can offset El Niño
In one line: The Indian Ocean Dipole (IOD) is the difference in sea surface temperature between the western Indian Ocean near Africa and the eastern Indian Ocean near Indonesia.
Phases
- Positive IOD: the west is warmer and the east cooler. This tends to bring more moisture and rain to India.
- Negative IOD: the reverse, which tends to reduce Indian rainfall.
The IOD usually develops around June and peaks between September and November.
Why it is in the news
In 1997 a strong positive IOD partly cancelled the effect of a powerful El Niño and India's monsoon stayed normal. In 2015 the IOD barely developed, and the monsoon was deficient. The explainer links the weak 2015 IOD to a shift in the westerly winds around Antarctica. UPSC asked about the IOD in Prelims 2017.
Where to go next
Madden-Julian Oscillation
The travelling rain band that shapes weeks of a monsoon
In one line: The Madden-Julian Oscillation (MJO) is an eastward-moving band of clouds and rain that circles the tropics every 30 to 60 days.
How it affects India
When the active, rainy phase of the MJO is over the Indian Ocean, it can strengthen monsoon rain and help form low-pressure systems. When it is far away, over Africa, the Americas or the Pacific, India can see long breaks in the monsoon. Unlike ENSO and the IOD, which act over a season, the MJO acts over weeks.
Why it is in the news
The explainer notes that in August 2023 the MJO stayed over Africa and the Americas, and India recorded its driest August since 1901. This is one reason 2023 ended below normal even though the IOD turned positive late in the season.
Where to go next
IMD monsoon forecasting
How India forecasts the season and why it can miss
In one line: The India Meteorological Department issues a long-range monsoon forecast in April, updates it at the end of May, and since 2021 has combined several global climate models.
How it works
The forecast is given as a percentage of the long-period average (LPA) of rainfall, with an error margin of a few percentage points. A season with rainfall at least 10% below the LPA is called deficient. IMD also gives regional forecasts for northwest, central, south peninsular and east and northeast India.
Why it is in the news
The 2026 monsoon ended with 759.4 mm of rain against a normal of 868.6 mm, 12.6% below normal. The explainer notes that some models expected a positive IOD while IMD's model expected a neutral one, and the IOD did not give a strong positive offset in 2026.
Where to go next
Take the 2 November 2026 quiz: 30 Prelims-style questions with answers