What are El Niño and La Niña?
El Niño is when the ocean along the equator in the eastern Pacific runs unusually warm; La Niña is when it runs cool. The Pacific is so big that this moves where tropical storms form, which bends the jet stream and shifts winter weather thousands of miles away.
Shifts the odds of a wet or dry, mild or cold winter.
Wet winters mean more mold and pollen later; dry ones, more dust and fire smoke.
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How it works
Normally the trade winds blow from east to west along the equator, piling warm surface water up near Indonesia and letting cold water well up off South America. That warm pool feeds huge thunderstorms in the western Pacific.
During El Niño the trades weaken, warm water sloshes east and the thunderstorms follow it. During La Niña the trades strengthen, the cold water off South America spreads west and the storms stay far west. Scientists track it with the ocean temperature in a patch of the central Pacific called Niño 3.4: about 0.5°C (0.9°F) warmer than normal for several months counts as El Niño, that much cooler as La Niña. Events come every two to seven years.
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What it usually does to US winters
- El Niño: the Gulf Coast from Texas to Florida turns wetter than average, the most reliable signal of all. The Ohio Valley tends to be drier. Southern California and the Southwest have better odds of a wet winter, but mainly in strong events; weak ones are a coin toss. The northern US often runs milder.
- La Niña: roughly the reverse: a drier, warmer South and Southwest, and a wetter, colder Pacific Northwest and northern tier.
These are odds, not promises. Any one winter can buck the pattern.
Right now
As of NOAA's 8 October 2026 discussion, an El Niño Advisory is in effect, with the central Pacific about 2°C above normal and a strong event likely to last through winter. Strong El Niños also tend to push global temperatures up for the following year.
Questions people ask
- Does El Niño mean a rainy winter in California?
- It raises the odds, especially in strong events, but doesn't guarantee it. Some strong El Niño winters have still come up short.
- Why is it called El Niño?
- Fishermen in Peru noticed warm water arriving around Christmas and named it after the Christ child, El Niño. La Niña, 'the girl', is its cool opposite.
- How often do El Niño and La Niña happen?
- Every two to seven years on average, usually peaking in late fall or winter and lasting nine to twelve months.