Record Pacific warmth signals a possible record-strength El Niño

Sources

• Meteored — YourWeather (Christian Garavaglia) · Reports preliminary daily 30.06°C for Niño 3.4 on 5 October 2026, based on NOAA OISST processed through Climate Reanalyzer; not independently verified against original daily NOAA dataset. · 8 October 2026
• International Research Institute for Climate and Society (IRI), Columbia University — October 2026 Quick Look · Original research-institution outlook; +3.3°C weekly reading and 27-model forecast. Research institute classified as newspaper because the portal lacks a research source type. · 19 October 2026
• Columbia University Center for Climate Systems Research — October 2026 ENSO Forecast · The 27-model forecast that all models predict very strong Niño 3.4 conditions through DJF 2026–27; academic forecast classified as newspaper because the portal lacks a research source type. · 19 October 2026
• World Meteorological Organization — Global Seasonal Climate Update, OND 2026 · Seasonal mean Niño 3.4 anomaly forecast at approximately +3.7°C for October–December 2026, projected to peak around December. · 8 October 2026
• NOAA Climate Prediction Center — ENSO Diagnostic Discussion · Independent official outlook, using NOAA strength thresholds/relative index; forecasts strong-to-very-strong El Niño, with uncertainty and differing model timelines. · 8 October 2026

Syllabus

Topics

Related previous-year questions

Asked in earlier UPSC Prelims papers on this topic. Answer, then check.

1. UPSC Prelims 2011 · Geography · Climatology

   La Nina is suspected to have caused recent floods in Australia. How is La Nina different from El Nino? 1. La Nina is characterised by unusually cold ocean temperature in equatorial Indian Ocean whereas El Nino is characterised by unusually warm ocean temperature in the equatorial Pacific Ocean. 2. El Nino has adverse effect on south-west monsoon of India, but La Nina has no effect on monsoon climate. Which of the statements given above is/are correct?

   1. 1 only
   2. 2 only
   3. Both 1 and 2
   4. Neither 1 nor 2
   Show answer

   Answer: D. Correct Answer: Neither 1 nor 2 Both statements are incorrect because they wrongly describe the location and monsoon impact of El Niño and La Niña. Statement-wise Explanation 1. Statement 1 — Incorrect El Niño and La Niña do not occur in the Indian Ocean. They occur in the central and eastern equatorial Pacific Ocean. They are opposite phases of the El Niño-Southern Oscillation (ENSO). El Niño: abnormal warming of surface waters in the central/eastern equatorial Pacific. La Niña: abnormal cooling of surface waters in the central/eastern equatorial Pacific. 2. Statement 2 — Incorrect La Niña does affect the Indian monsoon. The statement saying it has “no effect” is wrong. El Niño generally weakens the South-West Monsoon and may cause deficient rainfall or drought-like conditions in India. La Niña generally strengthens the South-West Monsoon and may cause above-normal rainfall, floods, and intense rainfall events. Extra UPSC Info ENSO has three phases: El Niño, La Niña, and Neutral phase. El Niño is linked with weak trade winds, reduced upwelling near South America, and warmer Pacific waters. La Niña is linked with stronger trade winds, stronger upwelling, and cooler Pacific waters. ENSO influences rainfall, droughts, floods, agriculture, food prices, and disaster management in India. A separate phenomenon called the Indian Ocean Dipole (IOD) occurs in the Indian Ocean. A positive IOD can sometimes reduce the negative impact of El Niño on the Indian monsoon. Final Takeaway El Niño and La Niña occur in the Pacific Ocean, not the Indian Ocean. Both affect the Indian monsoon, with El Niño generally weakening it and La Niña generally strengthening it. Therefore, the correct answer is Neither 1 nor 2.

   Difficulty: medium · statement

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2. UPSC Prelims 2017 · Geography · Indian Geography

   With reference to ‘Indian Ocean Dipole (IOD)’ sometimes mentioned in the news while forecasting Indian monsoon, which of the following statements is/are correct? 1. IOD phenomenon is characterised by a difference in sea surface temperature between tropical Western Indian Ocean and tropical Eastern Pacific Ocean. 2. An IOD phenomenon can influence an El Niño’s impact on the monsoon. Select the correct answer using the code given below:

   1. 1 only
   2. 2 only
   3. Both 1 and 2
   4. Neither 1 nor 2
   Show answer

   Answer: B. VERDICT: The answer is 2 only. An Indian Ocean Dipole event can influence El Nino's impact on the monsoon, but the temperature difference is within the Indian Ocean, not between it and the Pacific. ANALYSIS: Statement 1 is INCORRECT. The Dipole is an irregular oscillation of sea surface temperatures in which the western Indian Ocean becomes alternately warmer and then cooler than the eastern part of the same ocean. The statement wrongly places the second pole in the tropical eastern Pacific. Statement 2 is CORRECT. A positive Dipole can bring good rainfall to India even in an El Nino year, while a negative one can aggravate the El Nino effect, so it modulates that influence. SOURCE: Indian Express explainer on the Indian Ocean Dipole and the monsoon. Source type EM. HOW TO CRACK IT: The name contains the disproof, since Indian Ocean Dipole means two poles within the Indian Ocean, and a pole located in the Pacific would make it a different phenomenon altogether. Reading a scientific term as a description of its own geography is the quickest route here. Keep the Dipole and El Nino distinct but linked, because the examinable point is that the two interact rather than that either alone determines the monsoon.

   Difficulty: hard · statement

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3. UPSC Prelims 2020 · Geography · Oceanography

   With reference to Ocean Mean Temperature (OMT), which of the following statements is/are correct? 1. OMT is measured up to a depth of 26°C isotherm which is 129 meters in the south-western Indian Ocean during January–March. 2. OMT collected during January–March can be used in assessing whether the amount of rainfall in monsoon will be less or more than a certain long-term mean. Select the correct using the code given below:

   1. 1 only
   2. 2 only
   3. Both 1 and 2
   4. Neither 1 nor 2
   Show answer

   Answer: B. Statement 1 – INCORRECT: Ocean heat content (OHC) and Ocean Mean Temperature (OMT) are important climatic parameters required for atmospheric and oceanic studies like cyclone and monsoon predictions and ocean heat transport estimations. Sea surface temperature (SST) is routinely used for predicting whether the total amount of rainfall that India receives during the monsoon season will be less or more than the long-term mean. The SST is restricted to a few millimetres of the top ocean layer and is largely influenced by strong winds, evaporation, or thick clouds. In contrast, OMT, which is measured up to a depth of 26 degree C isotherm, is more stable and consistent. Statement 1's specific figure of '129 meters in the south-western Indian Ocean during January-March' cannot be verified as correct from the material. Hence statement 1 is not correct as stated. Statement 2 – CORRECT: Scientists from Pune's Indian Institute of Tropical Meteorology (IITM) find that ocean mean temperature (OMT) that has better ability to predict this than the sea surface temperature. Compared with SST which has 60% success rate of predicting the Indian summer monsoon, OMT has 80% success rate. OMT collected during January–March can thus be used in assessing whether the amount of rainfall in monsoon will be less or more than a certain long-term mean. Hence statement 2 is correct. Correct statement: 2 only → Option (b).

   Difficulty: hard · statement

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4. UPSC Prelims 2012 · Geography · Climatology

   Consider the following statements: 1. The duration of the monsoon decreases from southern India to northern India. 2. The amount of annual rainfall in the northern plains of India decreases from east to west. Which of the statements given above is/are correct?

   1. 1 only
   2. 2 only
   3. Both 1 and 2
   4. Neither 1 nor 2
   Show answer

   Answer: C. Correct Answer: Both 1 and 2 The Indian monsoon shows clear regional variation in both duration and rainfall amount. These patterns are mainly controlled by the arrival and withdrawal of the southwest monsoon and the movement of moisture-bearing winds. Statement-wise Explanation 1. The duration of the monsoon decreases from southern India to northern India — Correct The southwest monsoon reaches southern India first, around the beginning of June. It reaches northern India later and withdraws earlier. Therefore, the monsoon season is longer in southern India and shorter in northern India. 2. The amount of annual rainfall in the northern plains of India decreases from east to west — Correct The Bay of Bengal branch of the monsoon enters the northern plains from the east. As it moves westward, it gradually loses moisture. Hence, rainfall decreases from eastern areas like Assam, West Bengal and Bihar towards western areas like Delhi, Haryana and Rajasthan. Extra UPSC Info * The southwest monsoon has two main branches: Arabian Sea branch and Bay of Bengal branch. * The Arabian Sea branch gives heavy rainfall to the Western Ghats. * Tamil Nadu receives less rainfall during the southwest monsoon because it lies in the rain shadow region of the Western Ghats. * Tamil Nadu gets much of its rainfall during the retreating or northeast monsoon. * Western disturbances bring winter rainfall to north-western India, useful for Rabi crops like wheat. Final Takeaway Both statements are correct because monsoon duration decreases from south to north, while rainfall in the northern plains decreases from east to west.

   Difficulty: medium · statement

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5. UPSC Prelims 2026 · Geography · Indian Geography

   With reference to the climate of Andaman and Nicobar Islands, which of the following statements is/are correct? 1. The climate can be defined as a humid, tropical coastal climate. 2. It receives rainfall from both South-west monsoon and North-east monsoon. 3. Maximum precipitation is between December and May. Select the answer using the code given below:

   1. 1 only
   2. 1 and 2
   3. 2 and 3
   4. 3 only
   Show answer

   Answer: B. Statement 1 is correct: The islands have a tropical climate with warm summers and not so chill winters, which is described as a humid, tropical coastal climate. Statement 2 is correct: The Andaman and Nicobar Islands experience two monsoon phases. The Southwest Monsoon arrives in June, July, August and September, and the Northeast Monsoon arrives in October, November and December. During these periods the islands are blessed with heavy rainfall, which transforms the landscape into a lush, green wonderland. Statement 3 is not correct: Maximum precipitation is received during the Southwest Monsoon, not between December and May. Statements 1 and 2 are correct, so the answer is Option (b).

   Difficulty: easy · statement

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Practice questions

1. The Niño 3.4 region used to track El Niño lies in the:

   1. Western Pacific near Indonesia
   2. Central-eastern equatorial Pacific
   3. Indian Ocean
   4. North Atlantic
   Show answer

   Answer: B. Its temperature anomaly is the main index of ENSO strength.

   Difficulty: medium · statement

2. During El Niño, the Walker circulation over the Pacific:

   1. Strengthens
   2. Weakens and shifts eastward
   3. Reverses permanently
   4. Is unaffected
   Show answer

   Answer: B. Rising air moves towards the central Pacific.

   Difficulty: medium · statement

3. A positive Indian Ocean Dipole is associated with:

   1. Warmer western Indian Ocean relative to the east
   2. Warmer eastern Indian Ocean relative to the west
   3. Colder Arabian Sea
   4. Stronger La Niña
   Show answer

   Answer: A. It can support Indian monsoon rainfall.

   Difficulty: medium · statement

Mains practice

Answer-writing practice on this article. Attempt it first, then open the hints.

1. GS1 · 150 words

   Explain how El Niño influences the Indian monsoon. Why is the relationship not straightforward?

   Show hints

   1. Walker circulation, ENSO phases
   2. IOD
   3. timing and decay
   4. past exceptions such as 1997
   5. local factors.