WMO says El Niño will peak in December, with record Pacific warming forecast
The tropical Pacific may be headed for its warmest El Niño reading on record. What does that mean for India's winter?
Published 9 October 2026. Written by Pratidin from the reports linked at the end; every fact checked by a separate review before publishing. How we work
The World Meteorological Organization (WMO) said on 8 October 2026 that El Niño is firmly established and strengthening, and is expected to peak in December. Its Global Seasonal Climate Update for October to December 2026, based on a consensus of thirteen forecasting centres, gives a near-100% likelihood that El Niño persists through February 2027. Sea-surface temperatures in the central and eastern tropical Pacific are forecast to reach record levels. The WMO said the event is potentially one of the strongest since at least 1950, and Secretary-General Celeste Saulo said the ocean is "the warmest we've ever measured it."
The key measure is the Niño 3.4 index, the sea-surface temperature anomaly in the central equatorial Pacific. It rose from about +1.6°C above normal in June 2026 to +2.5°C in August. For October to December, the seasonal average is forecast near +3.7°C, which would be the highest since observations began; the previous record was +2.6°C, in November 2015 to January 2016. The WMO also expects a positive Indian Ocean Dipole (IOD) to peak in October and then decline, with a seasonal anomaly of about +0.5°C. August 2026 was the hottest August on record, and global sea-surface temperature reached an all-time observed high that month.
For October to December, the update shows drier than normal conditions as likely over the Indian subcontinent, the western Pacific and parts of South America, and wetter than normal conditions over the Greater Horn of Africa, parts of Central Asia and southeastern South America. It forecasts an overwhelming likelihood of above-average temperatures over large areas, raising the risk of heat extremes. Ms. Saulo noted that strong El Niño events often lead to very hot years, as happened in 2024, because El Niño releases heat stored in the ocean. The WMO stresses that these are seasonal likelihoods, not substitutes for national forecasts, which in India come from the India Meteorological Department.
Prelims facts
- The WMO expects El Niño to peak in December 2026 and gives a near-100% chance that it lasts through February 2027.
- The Niño 3.4 index is forecast near +3.7°C for October to December 2026, above the previous record of +2.6°C set in November 2015 to January 2016.
- A positive Indian Ocean Dipole is expected to peak in October 2026 and then decline.
- The WMO's October to December outlook shows drier than normal conditions as likely over the Indian subcontinent.
- The Global Seasonal Climate Update is issued monthly; WMO's El Niño/La Niña Update is quarterly.
Quick recall
- When does the WMO expect the 2026 El Niño to peak?
- December 2026.
- WMO's likelihood that El Niño persists through February 2027?
- Near 100%.
- Forecast Niño 3.4 average for October to December 2026?
- About +3.7°C above normal.
- Previous record Niño 3.4 value?
- +2.6°C, November 2015 to January 2016.
- When is the positive IOD expected to peak in 2026?
- October 2026, then decline.
- Who heads the WMO?
- Secretary-General Celeste Saulo.
- In a positive IOD, which side of the Indian Ocean is warmer?
- The western side.
- How often is WMO's Global Seasonal Climate Update issued?
- Monthly.
Prelims practice question
With reference to the Niño 3.4 index, which is used to track El Niño, consider the following statements:
1. It measures the sea-surface temperature anomaly in the central equatorial Pacific Ocean.
2. Its previous record value was set in the 1997-98 El Niño.
3. The WMO forecasts its October to December 2026 average to be the highest since observations began.
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: the WMO puts the previous record at +2.6°C in November 2015 to January 2016. Statement 3 is correct: the forecast of about +3.7°C would be the highest since observations began.
Use this in UPSC Mains: previous-year questions
Recurring theme: ENSO, the Indian Ocean Dipole and their impact on Indian weather
- How to use this
Use the 2026 forecast to show El Niño's real reach while arguing that factors like the Indian Ocean Dipole also shape outcomes, so not every anomaly is El Niño.
- The WMO forecasts the Niño 3.4 index near +3.7°C for October to December 2026, above the +2.6°C record of 2015-16.
- It links strong El Niño events to very hot years such as 2024, as stored ocean heat is released.
- A positive Indian Ocean Dipole, expected to peak in October 2026, can partly offset El Niño's drying of Indian rainfall.
Background on monsoon climate; the story is about a Pacific forecast, not monsoon characteristics.
The WMO update tracks a positive IOD alongside El Niño, the exact relationship this question tests.
Mains practice question
What is El Niño? Explain how a strong El Niño, together with the Indian Ocean Dipole, can affect India's weather and economy, in the light of the WMO's latest forecast. (250 words)
Model answer
El Niño is the warm phase of the El Niño Southern Oscillation (ENSO), when the central and eastern tropical Pacific becomes unusually warm and trade winds weaken. On 8 October 2026, the WMO said the current El Niño will peak in December, with a near-100% chance of lasting through February 2027.
The forecast
- Niño 3.4 index forecast near +3.7°C for October to December 2026, above the earlier record of +2.6°C (2015-16).
- A positive Indian Ocean Dipole peaking in October, about +0.5°C for the season.
- Drier than normal conditions likely over the Indian subcontinent in October to December.
How El Niño affects India
- Monsoon: El Niño shifts rising air and rainfall towards the central Pacific and is often linked to weaker Indian rainfall.
- Heat: strong El Niño years release ocean heat; the WMO links them to very hot years such as 2024.
- Agriculture: lower rain and heat stress affect rabi sowing, reservoir levels and food prices.
- Economy: food inflation and lower rural demand complicate monetary policy.
Role of the Indian Ocean Dipole
- A positive IOD (warmer western Indian Ocean) can offset part of El Niño's drying effect.
- The IOD is expected to decline after October, limiting this buffer.
Way forward
- Use IMD's regional forecasts for contingency crop plans.
- Protect reservoir storage, prepare heat action plans, and pre-position food stocks.
A record-strength El Niño is a slow-onset risk; early preparation can limit its cost.
The basics
Why this matters
El Niño is a warming of the tropical Pacific Ocean that changes weather across the world. In India it is closely watched because it is often linked to weaker rainfall and hotter conditions. The WMO now says the 2026 event could be the strongest on record by one key measure.
What happens in normal years
Over the equatorial Pacific, trade winds usually blow from east to west. They push warm surface water towards Indonesia and Australia, where air rises and rain falls. Cool, deep water wells up off South America. This east-west loop of air is the Walker circulation.
- 1Trade winds pile warm water in the western Pacific
- 2Trade winds weaken; warm water spreads east; rain shifts towards the central Pacific
- 3Warmth discharges and conditions drift back to neutral
- 4Trade winds strengthen; the eastern Pacific turns colder than normal
How El Niño is measured
Scientists track the Niño 3.4 index, the temperature anomaly of the sea surface in a box of the central equatorial Pacific. The bigger the positive anomaly, the stronger the El Niño.
The Indian Ocean's own see-saw
The Indian Ocean Dipole compares the western and eastern parts of the tropical Indian Ocean. When the west is warmer (a positive IOD), it can support rainfall over India and partly offset El Niño. The WMO expects this year's positive IOD to peak in October and then fade.
- Central and eastern Pacific warmer than normal
- Often linked to weaker rainfall in India
- Forecast to peak in December 2026
- Western Indian Ocean warmer than eastern
- Can partly offset El Niño's drying
- Forecast to peak in October 2026, then decline
Who forecasts what
The World Meteorological Organization combines forecasts from many centres into global outlooks. For India, the official forecasts come from the India Meteorological Department, and the WMO itself says its seasonal maps do not replace national forecasts.
Go deeper
In one line: The WMO expects El Niño to peak in December 2026, with the Niño 3.4 index forecast near +3.7°C, which would be a record.
Why it matters for UPSC
ENSO and the IOD are standard GS1 geography topics and frequent Prelims questions. A strong El Niño also feeds into GS3 themes: drought, heat, food inflation and disaster preparedness.
The core idea
El Niño weakens the Walker circulation over the Pacific, shifting rainfall east. Its strength is read from the Niño 3.4 index. India's rainfall also depends on the Indian Ocean Dipole, which can soften or worsen El Niño's effects. The World Meteorological Organization pools forecasts from many centres into its seasonal updates.
Numbers and dates to remember
- WMO update: 8 October 2026, covering October to December 2026
- Peak expected: December 2026; persistence through February 2027 near 100% likely
- Niño 3.4: about +1.6°C (June), +2.5°C (August), about +3.7°C forecast (October to December)
- Previous record: +2.6°C, November 2015 to January 2016
- Positive IOD: peak in October, about +0.5°C for the season
Where to go next
- Walker circulation: the Pacific air loop that El Niño disrupts
- Niño 3.4 index: how El Niño's strength is measured
- Indian Ocean Dipole: the Indian Ocean pattern that can offset El Niño
- World Meteorological Organization: the UN body behind the forecast
Go deeper: El Niño is not destiny
The link is strong but not fixed. El Niño years are often weak monsoon years for India, because the Walker circulation shifts and rising air moves away from the Indian region. But the relationship is not one-to-one. A positive Indian Ocean Dipole can bring extra moisture and partly offset El Niño, which is why forecasters track both together.
Why this event stands out. The Niño 3.4 index is forecast near +3.7°C for October to December 2026, well above the +2.6°C record of 2015-16. The WMO also notes that the ocean is the warmest ever measured, with August 2026 the hottest August on record. More stored heat means more heat to release into the atmosphere, raising the risk of heat extremes into 2027.
What the outlook says for India. The World Meteorological Organization update shows drier than normal conditions as likely over the Indian subcontinent from October to December, the season of the northeast monsoon over south-eastern India. It also expects the positive IOD to decline after October.
Limits of global outlooks. The WMO says its maps show likelihoods, not local forecasts. Policy decisions on crops, reservoirs and heat plans should rest on the India Meteorological Department's regional forecasts.
Walker circulation
The Pacific air loop that El Niño disrupts.
In one line: The Walker circulation is the east-west loop of air over the equatorial Pacific: rising over the warm west, flowing east aloft, sinking over the cool east and returning west as trade winds.
How it works in normal years
Trade winds push warm surface water towards Indonesia. Warm water heats the air above it, which rises and brings heavy rain to the western Pacific. Off South America, cold water wells up from the deep and the air sinks, keeping that coast dry.
What El Niño does
During El Niño, the trade winds weaken and warm water spreads east. The rising branch of the loop shifts towards the central Pacific, and rainfall follows it. Regions that depended on the old pattern, including parts of South and Southeast Asia, can turn drier.
Where to go next
Niño 3.4 index
How El Niño's strength is measured.
In one line: The Niño 3.4 index is the sea-surface temperature anomaly, the difference from normal, averaged over a box of the central equatorial Pacific between 5°N and 5°S and 170°W and 120°W.
How it is used
A sustained positive anomaly signals El Niño and a negative one La Niña. The larger the anomaly, the stronger the event. Agencies compare current values with past records to judge how unusual an event is.
Why it is in the news
The WMO says the index rose from about +1.6°C in June 2026 to +2.5°C in August, and is forecast near +3.7°C for October to December 2026. That would beat the previous record of +2.6°C, set in November 2015 to January 2016.
Where to go next
Indian Ocean Dipole
The Indian Ocean pattern that can offset El Niño.
In one line: The Indian Ocean Dipole (IOD) is the difference in sea-surface temperature between the western and eastern parts of the tropical Indian Ocean.
Positive and negative phases
In a positive IOD, the western Indian Ocean near Africa is warmer than the eastern part near Indonesia. This tends to favour rainfall over India. In a negative IOD, the pattern reverses.
Why it matters with El Niño
The IOD can influence El Niño's impact on the Indian monsoon. A positive IOD can partly cancel El Niño's drying effect, which is why forecasters watch both oceans.
Why it is in the news
The WMO expects a positive IOD to peak in October 2026 and then decline, with a seasonal anomaly of about +0.5°C.
Where to go next
World Meteorological Organization
The UN body behind the forecast.
In one line: The World Meteorological Organization (WMO) is the United Nations specialised agency for weather, climate and water, headquartered in Geneva.
What it does
The WMO coordinates national weather services, sets standards for observations and pools forecasts. Its monthly Global Seasonal Climate Update covers ENSO, the Indian Ocean Dipole and tropical Atlantic temperatures, and complements its quarterly El Niño/La Niña Update. India is represented through the India Meteorological Department.
Why it is in the news
Its update for October to December 2026, drawn from thirteen centres, forecasts a record El Niño peaking in December. Its Secretary-General, Celeste Saulo, called El Niño "firmly established and strengthening rapidly."
Where to go next
Take the 9 October 2026 quiz: 30 Prelims-style questions with answers