El Niño & La Niña (El Niño-Southern Oscillation)

Spherical map of the tropical Pacific showing colder than average sea surface temperatures at the equator in August 2020


La Niña—the cool phase of the El Niño-Southern Oscillation climate pattern—emerged in the tropical Pacific in August 2020. Forecasters estimate a 75% chance these conditions will last through Northern Hemisphere winter. La Niña winters tend to favor warm and dry conditions in the southern tier of the U.S.

Latest official ENSO update

Latest ENSO blog update

(image at left) Cooler-than-average surface waters in the central and eastern Pacific in August 2020 are one sign of La Niña. 

El Niño and La Niña are the warm and cool phases of a recurring climate pattern across the tropical Pacific—the El Niño-Southern Oscillation, or “ENSO” for short.

The pattern can shift back and forth irregularly every two to seven years, and each phase triggers predictable disruptions of temperature, precipitation, and winds.

These changes disrupt the large-scale air movements in the tropics, triggering a cascade of global side effects.

More about El Niño
What is El Niño in a nutshell?
Understanding El Niño (video)
ENSO alert system criteria
ENSO essentials
Educational Resources on ENSO

Globes showing typical climate impacts over the U.S. during El Niño and La Niñaca

El Niño is anchored in the tropical Pacific, but it affects seasonal climate "downstream" in the United States. In the summer, El Niño's primary influence on U.S. climate is on the hurricane season in both the eastern Pacific and the Atlantic. 

Typical ENSO impacts
Winter temperature and precipitation
Hurricane season impacts
Current outlooks
6-10 day outlook
8-14 day outlook
1-month outlook
3-month outlook

El Niño and La Niña have their strongest influence on global climate during the Northern Hemisphere winter. During La Niña winters, the southern tier of the United States is often drier than normal. Northern Australia, Indonesia, and the Philippines are often wetter than normal. 

More information
ENSO's cascade of global impacts
The Walker Circulation
More maps of global impacts of La Niña and El Niño

Cartoon representation of the interaction of ENSO and the MJO as boats creating overlapping wakes

Catch a wave: how waves from the MJO and ENSO impact U.S. rainfall

September 24, 2020

Guest blogger Marybeth Arcodia explains her latest research into how the Madden-Julian Oscillation and ENSO sometimes enhance each other's influence on U.S. precipitation and other times cancel each other out. Read more

(left) ENSO and the MJO both create atmospheric waves that ripple from the tropics to the mid-latitudes. Depending on how these waves overlap, they may enhance or cancel out each pattern's typical influence on U.S. precipitation.