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


La Niña—the cool phase of the El Niño-Southern Oscillation climate pattern—weakened through March 2021, and odds are good conditions will revert to normal in the next month or so. But the continued presence may tip the odds toward a more active severe weather season.

Latest official ENSO update

Latest ENSO blog update

(image at left) Map of March 2021 sea surface temperatures compared to average shows a large swath of cooler than average waters in the central-eastern tropical Pacific, one of the signs of La Niña. The cool anomaly was weaker than it was in February, however. 

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 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. In winter, it influences the jet stream and the path of storms that move from the Pacific over the United States. 

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

April 2021 ENSO update: spring triathlon

April 8, 2021

Conditions in the tropical Pacific Ocean are likely to transition from La Niña to neutral in the next month or so, but the fact that it is hanging on may tip the odds toward a more active U.S. severe weather season this year. Read more

(left) Subsurface temperatures in the tropical Pacific Ocean compared to average for a 5-day period centered on March 21, 2021. A large pool of warmer-than-average water beneath the surface indicates the current La Niña is weakening.