Current Monsoon Outlook

Southwest Monsoon Forecast: El Niño Threat Looms Over Tamil Nadu and Beyond

The India Meteorological Department (IMD) has projected that the 2026 southwest monsoon will deliver only about 90 % of the long‑period average rainfall, with June already lagging 40 % behind normal. The United Nations World Meteorological Organization warns that a moderate‑to‑strong El Niño‑Southern Oscillation could intensify, raising the risk of higher temperatures and erratic rains across the southern states that depend on the October‑December “winter” monsoon. With Tamil Nadu, Kerala and coastal Andhra Pradesh counting on this seasonal downpour for rabi crops, the forecast carries immediate food‑security and fiscal implications.

The IMD’s May 29 bulletin predicts that the monsoon will cover roughly half of India’s landmass by early July, a sharp contraction from the typical near‑nationwide spread at this stage. The agency expects June rainfall to reach at least 92 % of its climatological norm, but the current deficit suggests that the target is unlikely to be met.

• ▸June rainfall deficit exceeds 40 % of the long‑period average across the peninsular region.
• ▸Overall monsoon rainfall is projected at 90 % of the 1971‑2000 baseline.
• ▸Tamil Nadu historically receives 48 % (≈ 443 mm) of its annual rainfall during the October‑December window.

The shortfall threatens the rabi sowing calendar, potentially curbing wheat and oilseed yields that already face price pressures.

ENSO and Its Influence on Indian Rainfall

El Niño events raise sea‑surface temperatures in the eastern Pacific, weakening the low‑level westerly jet that feeds moisture into the Indian subcontinent. Conversely, a La Niña phase cools the same region, strengthening the jet and often delivering above‑average monsoon rains. Recent research by the Indian Institute of Tropical Meteorology (IITM) shows a Pearson correlation of –0.48 between Niño‑3.4 anomalies and All‑India Monsoon Rainfall, indicating that ENSO alone accounts for roughly 15 % of inter‑annual variability.

• ▸A single El Niño can lift 850 hPa geopotential heights by up to 4 gpm, shaving about 15 mm of precipitable water from the monsoon stream.
• ▸The 1997‑98, 2002‑03, 2015‑16 and 1991‑92 El Niño episodes each reduced JJAS (June‑September) rainfall by 10‑15 %.
• ▸The Madden‑Julian Oscillation (MJO) and the Indian Ocean Dipole modulate the timing of monsoon bursts, sometimes offsetting ENSO impacts.

Implications for Agriculture and the Economy

Rain‑deficient monsoons translate directly into reduced soil moisture, higher irrigation demand and lower crop output. The Reserve Bank of India’s recent “State of the Economy” note warned that a weak monsoon could add 0.2 percentage points to inflation and depress GDP growth by up to 0.4 % in the current fiscal year.

• ▸Rabi wheat acreage in Tamil Nadu and Kerala could fall by 12 % if rainfall remains below 80 % of normal.
• ▸Irrigation water withdrawals in the Cauvery basin are projected to rise by 5 % relative to 2025 levels.
• ▸The agricultural sector contributes roughly 17 % of India’s GDP; a 5 % dip in monsoon‑dependent output would shave about 0.85 % off national growth.

These pressures compound existing supply‑chain bottlenecks, potentially triggering higher food prices and widening fiscal deficits.

International Climate Commitments and India’s NDCs

India’s climate strategy under the UNFCCC and the Paris Agreement hinges on meeting its Nationally Determined Contributions (NDCs), which pledge a 30 % reduction in emissions intensity by 2030 and a 50 % increase in renewable electricity capacity. A monsoon shortfall undermines these targets by curtailing hydroelectric generation and increasing reliance on fossil‑fuel‑based irrigation pumps.

• ▸In 2025, monsoon‑driven hydroelectric output contributed 12 % of total renewable generation.
• ▸The NDC scenario assumes a 20 % rise in solar and wind capacity, but water‑stress could delay grid integration in southern states.
• ▸Failure to achieve the 2030 renewable target would expose India to heightened scrutiny under the global climate finance regime.

Balancing short‑term agricultural needs with long‑term decarbonisation will require adaptive water‑management policies, investment in climate‑resilient crop varieties, and accelerated deployment of off‑grid solar pumps.