Climate cycle
El Niño and La Niña
Every couple of years, the Pacific Ocean shifts. That shift ripples across weather worldwide for the next year. Here is what El Niño and La Niña actually do.
The definition
El Niño-Southern Oscillation (ENSO) is a cyclic pattern of ocean and atmospheric conditions in the tropical Pacific.
El Niño
Warmer sea surface in the eastern equatorial Pacific.
La Niña
Cooler sea surface in the eastern equatorial Pacific.
Neutral
Neither warm nor cool. Occurs about 30% of years.
The cycle averages 2-7 years. Not predictable more than 6-12 months out.
What El Niño does to US weather
Winter West Coast
Wetter. More storms. Better snowpack.
Winter Southern US
Wetter, cooler. More ice storms.
Winter Northern US
Milder, drier.
Winter Southeast
Wet and stormy.
Hurricane season
Fewer Atlantic hurricanes (upper shear suppresses).
Tornado season
Complicated. Often eastward shift.
Fire season West
Less severe due to wetter winter.
Alaska
Warmer.
What La Niña does to US weather
Winter West Coast
Drier. Especially Southern California.
Winter Southern US
Drier. Worse drought.
Winter Northern US
Colder, snowier.
Winter Southeast
Drier.
Hurricane season
MORE Atlantic hurricanes (less shear).
Tornado season
Complicated. Sometimes westward shift.
Fire season West
Worse due to drought.
Alaska
Colder.
The tornado season connection
- Research suggests weak La Niña winters produce more active spring tornado seasons in the traditional Alley.
- Strong El Niño winters may shift activity eastward.
- Neutral years show wide variability.
- This is a MODEST signal — not deterministic.
- Individual years vary a lot from the ENSO expectation.
The hurricane season connection
- El Niño: fewer Atlantic hurricanes. 8-12 named storms typical.
- La Niña: more Atlantic hurricanes. 14-20 named storms typical.
- Neutral: 12-15 named storms.
- El Niño creates upper shear that disrupts hurricane development.
- La Niña removes that shear.
- 2020, 2021, 2022, 2023 were all La Niña years — very active hurricane seasons.
- 2024 transitioned to neutral, then La Niña again.
The 1997-98 super El Niño
The strongest El Niño in modern record.
- California floods (Pineapple Express events).
- Winter storms damaging.
- Fewer Atlantic hurricanes (7 named).
- Ended severe drought in southwest.
- Approximately $10 billion economic impact.
- Warm winter in Northeast.
- Followed by strong La Niña 1998-2001.
The 2015-16 super El Niño
Similar strength to 1997-98.
- Massive California snowpack recovery.
- Ended California drought.
- Very quiet Atlantic hurricane season.
- Warm East Coast winter.
- Ice storms in Deep South.
The 2020-2023 triple-dip La Niña
First triple La Niña in modern record (since 1950).
- Very active Atlantic hurricane seasons.
- Extended Southwest drought.
- Cold winters Northern US.
- Difficult fire seasons West.
- Ended in early 2023.
How ENSO is forecast
- Sea surface temperature measurements (buoys, satellite).
- Subsurface ocean temperature.
- Trade wind measurements.
- Climate models trained on decades of data.
- NOAA CPC issues monthly ENSO outlooks.
- IRI (International Research Institute) also issues.
- Forecasts good 3-6 months ahead.
- Beyond 6 months: probabilistic.
Current status (as of 2026)
- Neutral to weak La Niña conditions.
- Ocean temperatures near average.
- Some models suggest ENSO transitions returning by 2026-27.
- Check climate.gov for current status.
- ENSO does not follow a set schedule.
The other oscillations
Pacific Decadal Oscillation (PDO)
Longer-term (20-30 year) Pacific temperature shift.
Atlantic Multidecadal Oscillation (AMO)
Similar for Atlantic. Affects hurricane activity.
North Atlantic Oscillation (NAO)
Pressure difference. Affects European weather.
Arctic Oscillation (AO)
Northern Hemisphere polar vortex strength.
Madden-Julian Oscillation (MJO)
30-60 day tropical wave.
Quasi-Biennial Oscillation (QBO)
Stratospheric wind shift every 28 months.