Climate Factor · Climate factor
El Niño–La Niña
Also known as: ENSO, El Niño-Southern Oscillation, La Niña
El Niño and La Niña are opposite phases of a recurring ocean-atmosphere pattern in the tropical Pacific, the El Niño-Southern Oscillation, that shifts rainfall and temperature patterns across many world regions on a multi-month to multi-year cycle, with effects that vary substantially by location.
The El Niño-Southern Oscillation (ENSO) describes a recurring variation in sea-surface temperature and atmospheric pressure across the tropical Pacific, oscillating between a warm phase (El Niño), a cool phase (La Niña), and a roughly neutral state in between. Climate agencies track ENSO status using sea-surface temperature indices and atmospheric pressure differences.
ENSO phase is associated with shifted odds of wetter or drier, and warmer or cooler, conditions in particular regions, such as parts of the Americas, Australia, Southeast Asia, and southern Africa. The specific regional effect, and its strength, differ by region and by individual event: ENSO influences probabilities and tendencies rather than guaranteeing a particular outcome in any given season.
What El Niño and La Niña are
El Niño and La Niña are opposite phases of the same underlying ocean-atmosphere oscillation in the tropical Pacific, distinguished by warmer or cooler than average sea-surface temperatures and corresponding shifts in atmospheric pressure and circulation.
- El Niño
- The warm phase of ENSO, associated with above-average sea-surface temperatures in parts of the tropical Pacific.
- La Niña
- The cool phase of ENSO, associated with below-average sea-surface temperatures in the same region.
- ENSO-neutral
- A state in which sea-surface temperatures and atmospheric conditions are near their long-term average, without a clear El Niño or La Niña signal.
How it is tracked
Meteorological and oceanographic agencies track ENSO using sea-surface temperature indices calculated for defined regions of the tropical Pacific, combined with atmospheric pressure differences between the eastern and western Pacific. These observations are supplemented by periodic model-based outlooks issued by national and international climate agencies.
Typical regional associations
| Region (general) | Commonly associated tendency |
|---|---|
| Parts of the southern United States and South America | Tendency toward wetter conditions during some El Niño events |
| Parts of Australia and Southeast Asia | Tendency toward drier conditions during some El Niño events |
| Same regions during La Niña | Often broadly opposite tendencies to El Niño, though not a mirror image in every case |
Why farmers and agencies monitor it
Seasonal outlooks that reference ENSO phase can inform agricultural risk planning, such as variety choice, planting timing, or water storage decisions. These outlooks describe shifted probabilities of certain conditions, not certain outcomes, and should be treated accordingly.
Limitations of ENSO-based outlooks
- Regional effects vary by event and are not identical from one El Niño or La Niña to the next
- Other climate drivers besides ENSO also influence any given season's weather
- Neutral periods and weak events tend to have less predictable regional effects
Relationships
Evidence-backed connections in the knowledge graph.
Scope & limitations
Geographic scope: A global ocean-atmosphere pattern with regionally specific effects; this entry does not provide region-specific forecasts or the current ENSO status.
- This is a general explainer, not a seasonal forecast or current ENSO status update.
- Regional effects vary by event and are expressed as shifted probabilities, not certainties.
Sources
This article draws on the following authoritative sources. See our sources & methodology for how they are selected.
- [1]NOAA — National Oceanic and Atmospheric Administration (opens in a new tab)Authoritative
U.S. National Oceanic and Atmospheric Administration (NOAA)
Cited for: ENSO monitoring, indices, and climate outlooks
- Type:
- Government agency
- Jurisdiction:
- United States
- Accessed:
- 2026-07-12
- [2]WMO — World Meteorological Organization (opens in a new tab)Authoritative
World Meteorological Organization (WMO)
Cited for: ENSO classification and international climate monitoring standards
- Type:
- Intergovernmental organization
- Jurisdiction:
- Global
- Accessed:
- 2026-07-12
- [3]FAO — Food and Agriculture Organization (opens in a new tab)Authoritative
Food and Agriculture Organization of the United Nations (FAO)
Cited for: ENSO-related agricultural risk and seasonal planning context
- Type:
- Intergovernmental organization
- Jurisdiction:
- Global
- Accessed:
- 2026-07-12
- Authoritative
Cited for: Rainfall variability and water availability context
- Type:
- Intergovernmental organization
- Jurisdiction:
- Global
- Accessed:
- 2026-07-12