Southwest Monsoon 2026: El Niño Threat and 41% Rainfall Deficit — Tamil Nadu Sees Strengthened Activity from June 20

Detailed Summary

India faced a significant rainfall deficit of approximately 41% as of June 19, 2026, as the Southwest Monsoon stalled over Maharashtra. The India Meteorological Department (IMD) reported region-wise deficits: central India 67%, east and northeast India 42%, south peninsula 22%, and northwest India 6%. However, there was positive news for Tamil Nadu — the IMD's Regional Meteorological Centre (RMC) in Chennai forecast enhanced monsoon activity from June 20–21, 2026. Upper-air circulation and a trough were influencing southern India, bringing widespread rainfall. Heavy rain was forecast for districts including Nilgiris, Erode, Salem, Dharmapuri, Krishnagiri, Coimbatore, Theni, and Dindigul. Meanwhile, the Southwest Monsoon 2026 arrived in Kerala on June 4, three days behind its normal date of June 1.

Tamil Nadu Monsoon Activity (June 20–21, 2026)

• Kalasapakkam (Tiruvannamalai district) recorded the highest rainfall: 9 cm in 24 hours ending 8:30 AM on June 21.
• Kakkudi (Ramanathapuram) received 8 cm of rainfall in the same period.
• IMD forecast heavy rain in Western Ghats districts: Nilgiris, Erode, Salem, Coimbatore, Theni, Dindigul, Dharmapuri, Krishnagiri.
• Chennai was expected to see improved monsoon conditions from June 21.
• Temperatures expected to drop by 4–5 degrees Celsius across several districts.
• Fishermen advised caution due to squally winds of 40–50 kmph along the Tamil Nadu coast, Gulf of Mannar, and Comorin areas.

Historical Background

The Southwest Monsoon (June–September) is the primary source of rainfall for India, contributing approximately 70–80% of the country's annual rainfall. It enters India through Kerala around June 1 (normal date) and covers the entire country by July 15. Tamil Nadu receives rainfall from both the Southwest Monsoon (June–September) and the Northeast Monsoon (October–December). The Northeast Monsoon, also called the "retreating monsoon," is the primary source of rainfall for Tamil Nadu, delivering 60% of the state's annual rainfall.

El Niño and Its Impact

IMD forecast that El Niño conditions would develop during the 2026 Southwest Monsoon season. El Niño is a periodic warming of equatorial Pacific Ocean surface temperatures that typically weakens the Indian Southwest Monsoon, causing below-normal rainfall. The 2026 Southwest Monsoon was forecast at 90% of the Long Period Average (LPA) — categorised as below-normal. NOAA (US National Oceanic and Atmospheric Administration) warned the 2026 El Niño could be one of the strongest on record, potentially persisting through Northern Hemisphere winter 2026-27.

IMD Monsoon Data

Tamil Nadu Relevance

Tamil Nadu's agriculture depends critically on both Southwest and Northeast Monsoons. The state grows rice in the Cauvery delta (Thanjavur, Tiruvarur, Nagapattinam — the "Granary of South India"). Erratic monsoon directly affects paddy cultivation. Tamil Nadu's main reservoirs — Mettur Dam (Stanley Reservoir), Mullaiperiyar, Krishnagiri, Sathanur — are replenished by monsoon rains. The state government monitors reservoir levels and alerts farmers through the Agriculture Department.

Important Facts

• Normal date of Southwest Monsoon onset in Kerala: June 1
• 2026 onset in Kerala: June 4 (3 days late)
• 2026 monsoon forecast: 90% of Long Period Average (below-normal)
• El Niño year: typically causes below-normal rainfall in India
• Tamil Nadu's Northeast Monsoon: October–December (primary rainfall season)
• IMD HQ: New Delhi; RMC Chennai covers Tamil Nadu and Puducherry

Organisations Involved

• India Meteorological Department (IMD) — National weather forecasting agency; HQ: New Delhi
• Regional Meteorological Centre (RMC) Chennai — Issues weather forecasts for Tamil Nadu
• NOAA (USA) — Issues global El Niño forecasts
• WMO (World Meteorological Organization) — UN body for weather and climate; HQ: Geneva

Related Static GK

IMD was established in 1875. India's Long Period Average (LPA) for Southwest Monsoon is 87 cm. Tamil Nadu's average annual rainfall is approximately 925 mm. Mettur Dam (Stanley Reservoir) on the Cauvery River is one of the largest dams in Tamil Nadu, located in Salem district. The Nilgiris receives the highest rainfall in Tamil Nadu — over 2,500 mm annually. Tamil Nadu is bounded by the Bay of Bengal to the east and the Arabian Sea to the west (Gulf of Mannar).

Important Terms

• El Niño: Warming of central and eastern Pacific Ocean surface temperatures — weakens Indian monsoon.
• La Niña: Cooling of Pacific — strengthens Indian monsoon.
• Long Period Average (LPA): Average monsoon rainfall calculated over 50 years — currently 87 cm.
• Parametric Trigger: Pre-set measurable condition (like temperature or rainfall level) that automatically triggers insurance payouts.

Exam-Oriented Notes

• Southwest Monsoon 2026 arrived in Kerala on June 4 — 3 days late.
• India faced 41% rainfall deficit as of June 19, 2026.
• El Niño typically weakens Indian monsoon.
• Tamil Nadu's primary monsoon: Northeast Monsoon (Oct–Dec).
• Tamil Nadu districts heavy rain (June 20–21): Nilgiris, Erode, Salem, Coimbatore, Theni, Dindigul, Dharmapuri, Krishnagiri.

3 TNPSC-Style MCQs

Q1. As of June 19, 2026, what was the approximate all-India rainfall deficit reported by IMD?

• A) 22%
• B) 30%
• C) 41%
• D) 67%

Answer: C) 41%
Explanation: IMD reported India was facing a 41% rainfall deficit as the Southwest Monsoon stalled over Maharashtra. The 22% deficit was for the southern peninsula and 67% for central India.

Q2. Which of the following statements about Tamil Nadu's monsoon pattern is correct?

• A) Tamil Nadu receives most of its rainfall from the Southwest Monsoon (June–September)
• B) Tamil Nadu's primary rainfall season is the Northeast Monsoon (October–December)
• C) Tamil Nadu does not receive any rainfall from the Southwest Monsoon
• D) Tamil Nadu receives equal rainfall from both monsoons

Answer: B) Tamil Nadu's primary rainfall season is the Northeast Monsoon (October–December)
Explanation: Unlike most of India, Tamil Nadu receives the majority (about 60%) of its annual rainfall from the Northeast Monsoon, not the Southwest Monsoon.

Q3. Which district recorded the highest rainfall in Tamil Nadu during the 24 hours ending June 21, 2026?

• A) Chennai
• B) Coimbatore
• C) Tiruvannamalai
• D) Ramanathapuram

Answer: C) Tiruvannamalai
Explanation: Kalasapakkam in Tiruvannamalai district recorded the highest rainfall of 9 cm in 24 hours ending 8:30 AM on June 21, 2026.