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La Niña
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World map illustrating the generalized weather effects of La Nina from December through February. The map highlights regions experiencing wet, dry, cool, or warm conditions, such as wet and cool in southeastern Africa and Australia, dry in equatorial Africa, cool in northern North America and parts of South America, and dry and cool across the central Pacific. Diagram of the equatorial Pacific Ocean showing El Nino conditions, with weak trade winds, increased rainfall over South America, increased convection, a deepened thermocline, and suppressed upwelling.
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World map illustrating the generalized weather effects of La Nina from December through February. The map highlights regions experiencing wet, dry, cool, or warm conditions, such as wet and cool in southeastern Africa and Australia, dry in equatorial Africa, cool in northern North America and parts of South America, and dry and cool across the central Pacific.
La Niña is associated with substantial changes to established weather patterns between December and February The weather effects of La Niña include increased rainfall in Southeast Asia, northern Australia, and the maritime continent, cooler and drier conditions in the eastern equatorial Pacific, cooler conditions in parts of Africa, northeast Asia, and western North America, and increased precipitation in parts of several continents, especially in southeastern Africa and in the middle latitudes of North America.

La Niña

oceanic phenomenon
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News •

Scientists trace record Arctic sea ice loss to an unexpected ocean • Oct. 29, 2026, 3:44 PM ET (Earth.com)
Scientists find key to predicting some El Niño events 12 months ahead • Oct. 23, 2026, 2:00 PM ET (Phys.org)

La Niña, the cool phase of El Niño and the Southern Oscillation (ENSO), characterized primarily by colder-than-normal surface waters of the Pacific Ocean along the western coast of South America, stronger-than-normal trade winds that drive warmer toward equatorial parts of Asia and northern Australia, and amplified nutrient upwelling along the South American coast (see also marine ecosystem: upwelling). While its local and regional effects on weather and climate are generally the opposite of those associated with El Niño, its global effects can be more complex. La Niña events often follow El Niño events, which occur at irregular intervals of about two to seven years.

The Oceanic Niño Index (ONI), a measure of the departure from normal sea surface temperature in the east-central Pacific Ocean, is the standard means by which each La Niña episode is determined, gauged, and forecast. La Niña episodes are indicated by sea surface temperature decreases of more than 0.5 °C (0.9 °F) for at least five successive overlapping three-month seasons.

The Editors of Encyclopaedia BritannicaThis article was most recently revised and updated by Rick Livingston.