Why this El Nino has hit India's monsoon so hard

The central Pacific is running 2.1°C warmer than normal, and the Indian Ocean pattern that protected India in 1997 came too late this year.

Global satellite map showing sea-surface height anomalies during the 2026 El Nino, dated October 12, 2026, with a deep purple band west of the dateline and a red-white band off South America

Sea-surface height anomaly in the equatorial Pacific, October 12, 2026NASA/JPL-Caltech, Sentinel-6 Michael Freilich

Published on:

27 Oct 2026, 11:50 am

India's 2026 southwest monsoon ended 12.6% below normal, the weakest season since 2015. Behind the shortfall is a warming of the equatorial Pacific Ocean, thousands of kilometres away, and an Indian Ocean pattern that came too late to help this time.

What El Nino is

El Nino is the warm phase of a natural climate cycle in the tropical Pacific. Every few years, surface waters in the central and eastern Pacific become unusually warm, and that changes where the heaviest rain-bearing clouds form. For India, the shift usually means a weaker monsoon.

Scientists track it through the Nino-3.4 region, a band of the central equatorial Pacific. On October 8, sea-surface temperatures there were 2.1°C above normal — in the "strong" El Nino range, according to the US Climate Prediction Center’s (CPC) ENSO Diagnostic Discussion of October 8, 2026.

Chart showing Nino-3.4 sea-surface temperature anomaly at +2.1C, in the strong El Nino range

Nino-3.4 sea-surface temperature anomaly, Oct 8 2026Graphic: The Pioneer, data: NOAA CPC

How strong, and for how long

NOAA’s Climate Prediction Center puts the odds at 83% that El Nino reaches "historic" strength — a three-month sea-surface-temperature anomaly of 2.5°C or more, stronger than any event since 1950 — for the October-December 2026 window. The chances are 54% for September-November and 70% for November-January, reflecting an event expected to peak around the turn of the year.

The World Meteorological Organization goes further: in a September 3, 2026 update, it put the likelihood of El Nino persisting through February 2027 — covering the whole rabi growing season — at "exceptionally high... nearly 100%", the most unequivocal such forecast in its history.

Bar chart of 54%, 83% and 70% odds of a historic El Nino across three overlapping forecast windows

Odds of El Nino reaching historic strength, by three-month windowGraphic: The Pioneer, data: NOAA CPC / WMO

The 1997 contrast

A strong El Nino does not guarantee a failed monsoon. In 1997, during one of the strongest El Nino events on record, a positive Indian Ocean Dipole (IOD) helped keep India's monsoon rainfall close to normal. In a positive IOD, the western Indian Ocean runs warmer than the eastern side.

This year the IOD arrived too late in the season to provide the same cushion.

Text comparison card contrasting the 1997 and 2026 El Nino monsoon outcomes

1997 vs 2026: how the Indian Ocean Dipole changed the outcomeGraphic: The Pioneer

The shortfall in numbers

India received 759.4mm of rain over the monsoon season, against a normal of 868.6mm — a shortfall of 12.6%. Seventeen of the country's 36 meteorological subdivisions ended the season with deficient rainfall.

The regional split was sharp. According to IMD’s own “Salient Features of the 2026 Southwest Monsoon Season” report (September 30, 2026), East and northeast India received just 74% of its long-period average rainfall (a 26% deficit) and the south peninsula 76% (24% short) — both in the “deficient” band — while northwest India (94% of LPA, 6% short) and central India (97% of LPA, 3% short) stayed in the normal range. Of the country’s 36 meteorological subdivisions, 17 (42% of the area) ended deficient, 18 (53% of the area) were normal, and one — Odisha — recorded excess rainfall.

The effects can now be seen in falling reservoir levels and in drought declarations across Karnataka, Maharashtra, Andhra Pradesh and Telangana.