Southwest Monsoon
Mechanism and Significance
The Southwest (SW) Monsoon is the primary rainfall system of India, responsible for about 70–75% of India's annual precipitation and critical for agriculture, hydropower, and groundwater recharge.
- Season: June 1 (normal Kerala onset) to September 30
- Mechanism: Driven by differential heating between the Indian landmass and the Indian Ocean. As the Indian subcontinent heats rapidly in summer, a low-pressure zone forms, drawing moisture-laden winds from the southwest off the Arabian Sea and Bay of Bengal.
- Two branches: (1) Arabian Sea branch — hits Kerala/Karnataka/Goa first, then moves north; (2) Bay of Bengal branch — hits northeast India/Bangladesh, then moves west
- Coverage: The monsoon normally covers the entire country by mid-July
- LPA (1971–2020): The Long Period Average of monsoon seasonal rainfall over India is 870 mm
- IMD Classification bands:
- Above Normal: 104–110% of LPA
- Normal: 96–104% of LPA
- Below Normal: 90–96% of LPA (the 2026 forecast at 92% falls here)
- Deficient: Below 90% of LPA
● Tracked since April 07, 2026 · last seen June 30, 2026 · updates as the daily brief publishes
30 Jun '26
India's June 2026 Monsoon Deficit: El Niño, MJO, and the Physics of a Weak Monsoon
Geography
11 Jun '26
El Niño Confirmed, Positive IOD Expected by July: Monsoon Outlook for 2026
Environment & Ecology
26 May '26
Southwest Monsoon 2026: IMD's Kerala Onset Forecast and What It Signals
International Relations
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