---
title: "Indian Summer Monsoon: UPSC GS1 Geography | Model Diplomat"
description: "The Indian Summer Monsoon is India's June–September southwest rainfall season supplying ~75% of annual rain. Mechanisms, onset dates, and UPSC GS1 relevance."
url: "https://modeldiplomat.com/learn/glossary/indian-summer-monsoon"
---

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Model Diplomat Research Team · Last reviewed June 22, 2026

TL;DR

- The Indian Summer Monsoon is the seasonal southwesterly airflow that delivers roughly 75 percent of India's annual rainfall between June and September.
- Why does the Indian Summer Monsoon split into two branches?
- How does El Niño affect the monsoon, and can the Indian Ocean Dipole offset it?
- What is the difference between the southwest and northeast monsoon?
- What are active and break periods of the monsoon?

[Civil Service & Diplomatic Exams](https://modeldiplomat.com/learn/civil-services/glossary)Updated June 22, 2026

The Indian Summer Monsoon is the seasonal southwesterly airflow that delivers roughly 75 percent of India's annual rainfall between June and September.

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In June 2023, the India Meteorological Department declared monsoon onset over Kerala on 8 June, a week later than normal, attributing the delay to El Niño conditions and Cyclone Biparjoy in the Arabian Sea.

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