# South Asia monsoon > The seasonal wind reversal delivering 75-90% of annual rainfall to nine countries between June and September, driving food security, flood risk, and public health across South Asia. **Meta:** type: reference · date: 2026-07-03 · heads: · 4 takes · 1 lenses · 2 regions ## What it is The South Asia monsoon is the seasonal reversal of atmospheric circulation that delivers 75-90% of annual precipitation across the region from June through September. Nine countries depend on it: Afghanistan, Bangladesh, Bhutan, India, Maldives, Myanmar, Nepal, Pakistan, and Sri Lanka, together home to roughly 1.9 billion people. The mechanism is the northward migration of the Intertropical Convergence Zone (ITCZ) in Northern Hemisphere summer, amplified by the temperature differential between the Indian Ocean (around 28°C) and the South Asian landmass (around 45°C at peak). India's Meteorological Department (IMD) declares onset when sustained Kerala rainfall covers the state for two consecutive days, lower-tropospheric westerly winds exceed 15-20 knots, and cloudiness crosses a defined threshold. The normal onset date is June 1 over Kerala; the monsoon covers all of India by mid-July via two branches, the Arabian Sea branch and the Bay of Bengal branch. ## History Monsoon variability has shaped South Asian civilizations for millennia. The IMD, founded in 1875, emerged partly from British colonial administrators tracking monsoon performance as a famine proxy. The crop failures of 1876-78 contributed to a famine killing an estimated 6-10 million people across India. El Niño episodes have repeatedly suppressed the season: the 2002 episode produced India's worst drought in 15 years; the 2009 episode cut the seasonal total to 78% of the long-period average. La Niña phases in 2010 and 2022 drove catastrophic flooding in Pakistan. The Indian Ocean Dipole (IOD), first characterized scientifically in 1999, modulates the season independently of ENSO: a positive IOD draws moisture toward East Africa, weakening South Asian rainfall; a negative IOD intensifies Indian Ocean convection and tends to bring above-normal monsoon totals. ## Current state For the June-September 2026 season, the South Asian Climate Outlook Forum (SACOF), coordinated by the World Meteorological Organization (WMO), forecast below-normal rainfall across most of South Asia, with the strongest deficit signal over central regions. The primary driver is an El Niño episode assessed at 80% probability for June-August 2026, rising above 90% through at least November. India's IMD separately forecast 92% of the long-period average (LPA), with a model error of plus or minus 5%. June 2026 became the driest in 146 years of Indian records: only 53.1 mm fell from June 4-22 against a normal 97.6 mm, a 46% deficit, delaying kharif planting across Maharashtra, Gujarat, and Madhya Pradesh. By early July 2026 the monsoon had advanced into Uttar Pradesh, Rajasthan, and Haryana, but the cumulative season deficit persisted. The [印度2026年季风创146年最干6月，卡里夫作物面临风险](/zh/n/india-monsoon-2026-kharif) and [季风停滞，印度迎来146年来最干旱的6月，卡里夫作物受威胁](/zh/n/india-driest-june-monsoon-kharif-2026) nodes track the unfolding crop impact in detail. ## Relationships The monsoon drives South Asia's kharif crop cycle (sown June-July, harvested September-October), covering rice, cotton, soybean, and groundnut. India produces around 23% of the world's rice; delayed rainfall compresses the planting window and lifts commodity prices regionally and globally. Monsoon-driven standing water creates mosquito-breeding conditions: Sri Lanka's mid-2026 dengue outbreak, with 44,000+ cases and 28 deaths by late June, was attributed partly to monsoon rains and cyclone debris, as tracked in [Sri Lanka's dengue surge](/zh/n/sri-lanka-dengue-surge-jun26). Hydropower generation in Nepal and Bhutan depends heavily on seasonal river volumes. Urban drainage in Mumbai, Dhaka, and Karachi is routinely overwhelmed in above-normal seasons, contributing to infrastructure losses worth billions of dollars. ## What to watch The 2026 El Niño trajectory is the key variable: an intensification toward 2015-16 strength could push India's seasonal total well below 90% of LPA, triggering government export restrictions on rice or wheat. IMD's monthly sub-divisional forecasts, released through September, will determine whether the June 2026 deficit is recovered during July-August and what the outlook is for the rabi (winter crop) planting window. Pakistan and Bangladesh face flash-flood risk even in below-normal mean seasons, as El Niño conditions concentrate rainfall in short, intense bursts along the Bay of Bengal branch. India's monthly Food Corporation of India stock data is a leading indicator for whether export policy shifts, and WMO's 2026 year-end State of Climate in Asia assessment will rank the season against the worst El Niño-driven droughts since 1950. ## Regional takes (batched by bias / lens) ### official record - **India Meteorological Department** (South Asia, en) — IMD live monsoon tracking portal covering onset declarations, daily progress maps, ENSO and IOD index monitoring, extended-range forecasts, and sub-divisional rainfall analysis. As of July 3 2026 the monsoon had advanced into parts of Gujarat, Madhya Pradesh, Haryana, and Rajasthan. Source: https://mausam.imd.gov.in/responsive/monsooninformation.php - **World Meteorological Organization** (South Asia, en) — SACOF April 30 2026 seasonal outlook: below-normal June-September rainfall across most of South Asia, strongest deficit signal in central regions, driven by El Nino at 80%+ probability through June-August 2026 and a positive Indian Ocean Dipole. Nine-country participation. Source: https://wmo.int/media/news/south-asia-expected-receive-below-average-monsoon-rainfall - **World Meteorological Organization** (Asia, en) — WMO annual climate review for Asia 2025: above-normal monsoon season caused devastating flooding in Pakistan, Sri Lanka, and Vietnam, confirming Asia recorded one of its hottest years on record with monsoon and cyclone-related rainfall a primary driver of extreme-weather damage. Source: https://wmo.int/resources/publication-series/state-of-climate-asia/state-of-climate-asia-2025 - **India Ministry of Earth Sciences / PIB** (South Asia, en) — IMD updated long-range forecast released May 29 2026: seasonal rainfall projected at 90% of the Long Period Average with a model error of plus or minus 4%, 60% probability of a deficient season, El Nino expected to intensify and persist into Northern Hemisphere winter 2026-27. Source: https://www.pib.gov.in/PressReleasePage.aspx?PRID=2266479®=3&lang=1 ## Across the graph - Related: [[india-monsoon-2026-kharif]], [[india-driest-june-monsoon-kharif-2026]], [[sri-lanka-dengue-surge-jun26]] - Entities: South Asia Monsoon, India, Country:pakistan, Commodity:rice, El Nino --- Canonical: https://rbtfl.xyz/zh/n/south-asia-monsoon-dossier