The cool phase of ENSO — Pacific surface temperatures fall below normal. Generally strengthens the Indian monsoon and intensifies Bay of Bengal cyclone activity.
PhenomenaWhat is La Niña?
La Niña (“the little girl” in Spanish) is the cool phase of the El Niño–Southern Oscillation (ENSO) climate cycle. During La Niña, surface waters of the central and eastern tropical Pacific Ocean become significantly cooler than average — typically by 0.5°C to 2°C below the long-term mean.
It is the opposite of El Niño in nearly every way. Where El Niño weakens monsoons, La Niña strengthens them. Where El Niño brings drought to Australia, La Niña brings flooding. The two phases together — with neutral conditions in between — form the single largest source of year-to-year climate variability on Earth, second only to the seasonal cycle.
For South Asia, La Niña years are usually welcome news: above-normal monsoon, better harvests, cooler pre-monsoon temperatures, fuller reservoirs. But La Niña also brings more Bay of Bengal cyclone activity, heavier monsoon flooding and tougher conditions for fishermen.
How La Niña works
During neutral conditions, trade winds blow east-to-west across the equatorial Pacific. Warm surface water piles up in the western Pacific (around Indonesia, Philippines). Cool deep water rises along the South American coast (Peru, Ecuador).
During La Niña, trade winds strengthen:
- Warm water is pushed even further west, intensifying the western Pacific warm pool.
- The eastern Pacific cools, with vigorous upwelling along South America.
- The Walker Circulation intensifies — rising air over Indonesia/SE Asia, sinking air over the eastern Pacific.
- Convection (storms, rainfall) shifts westward and intensifies over the Indian-Pacific tropical belt.
The result: the Asian summer monsoon is energised, and Indonesia, the Philippines, Bangladesh, eastern India and northeast Australia get more rainfall than normal.
La Niña’s impact on South Asia
The relationship between La Niña and the Indian monsoon is statistically positive but, like El Niño, not deterministic.
Typical La Niña effects in India:
- Above-normal southwest monsoon (June–September).
- Earlier or on-time monsoon onset over Kerala.
- More tropical depressions in the Bay of Bengal during monsoon.
- More intense Bay of Bengal cyclones in pre- and post-monsoon.
- Cooler pre-monsoon (April–May) — fewer extreme heatwaves.
- Drier winter (December–February) — less western-disturbance precipitation over northwest India.
Notable La Niña years and Indian monsoon:
- 1988: Strong La Niña; monsoon 19% above normal — major surplus.
- 1998–99: Moderate La Niña; near-normal monsoon.
- 2010: Moderate La Niña; monsoon 2% above normal.
- 2011: Strong La Niña; monsoon near-normal.
- 2020-23 “triple dip”: Three consecutive years of La Niña — only the third triple-dip on record, after 1973–76 and 1998–2001. Monsoons were near-normal to above-normal each year.
Bangladesh and Pakistan:
- Bangladesh: La Niña years often see heavier flooding in low-lying delta districts.
- Pakistan: Monsoon enhancement extends west; 2022 Pakistan super-floods occurred during La Niña, contributing to record monsoon rainfall.
La Niña’s impact on Southeast Asia
Southeast Asia experiences reliably wetter conditions during La Niña:
- Indonesia, Malaysia, Philippines: Heavy rainfall, often flooding.
- Thailand, Vietnam, Cambodia: Wetter monsoon than normal.
- Philippines: More typhoons making landfall (e.g., 2020 Typhoon Goni, the strongest landfalling typhoon on record by JTWC’s one-minute winds, occurred during La Niña).
- Northeast Australia: Severe flooding — the 2010-11 Queensland floods were a textbook La Niña event.
La Niña and Bay of Bengal cyclones
The Bay of Bengal is more cyclone-active during La Niña because:
- Sea-surface temperatures stay higher for longer.
- Wind shear is weaker, supporting cyclogenesis.
- Monsoon trough is more active.
Several deadly Bay of Bengal cyclones occurred during La Niña years:
- Cyclone Sidr (November 2007) — strong La Niña.
- Cyclone Aila (May 2009) — La Niña-to-neutral transition.
- Cyclone Yaas (May 2021) — La Niña.
La Niña and the 2026 monsoon
After the 2023-24 El Niño ended in mid-2024, a La Niña that emerged in December 2024 gave way to ENSO-neutral in March 2025, and the Pacific returned to weak La Niña from September 2025 into early 2026. That La Niña did not last: NOAA’s Climate Prediction Center reported ENSO-neutral conditions by April 2026 and El Niño conditions by June 2026, still strengthening in October 2026. IMD’s forecasts for the season were:
- 2026 monsoon onset: forecast for 26 May (± 4 days); the monsoon actually set in over Kerala on 4 June 2026, 3 days after the normal date of 1 June.
- Total monsoon rainfall: forecast in April 2026 as below normal, 92% of the long period average (LPA) ± 5%; the season ended at 87% of LPA.
Frequently asked questions
Is La Niña happening in 2026? Only early in the year. In early 2026 the Pacific was in weak La Niña or neutral conditions following the strong 2023-24 El Niño; by April 2026 these were giving way to ENSO-neutral, and El Niño formed in June and was strong by the end of the monsoon season. NOAA’s CPC and IMD update monthly.
Does La Niña always mean a good monsoon? Not always. The Indian Ocean Dipole (IOD) and MJO can amplify or suppress the effect.
What is a “triple dip” La Niña? Three consecutive La Niña years — extremely rare. The 2020–23 episode was only the third triple dip on record, after 1973–76 and 1998–2001, contributing to record monsoon flooding in Pakistan (2022) and Bangladesh (2020, 2022).
Does La Niña cause more cyclones? Yes — Bay of Bengal cyclones are more active during La Niña. Atlantic hurricanes are also more frequent. The reason is reduced wind shear in tropical regions.
Where can I see how La Niña is affecting my city? Mausam Online shows live weather and AQI on every city page. For seasonal context, see our Monsoon India 2026 guide (Hindi) and live forecasts for Mumbai, Kolkata, Dhaka, Chennai.