The Basics
El Niño is a climate pattern that occurs when sea surface temperatures in the central and eastern Pacific Ocean become unusually warm. It is one half of ENSO — the El Niño-Southern Oscillation — and typically occurs every 2-7 years, lasting 9-12 months.
What Happens During El Niño
Normally, trade winds blow warm water westward across the Pacific, keeping the eastern Pacific (off South America) cool. During El Niño, these trade winds weaken. Warm water spreads eastward, disrupting atmospheric circulation patterns globally.
Global Effects
| Region | El Niño Impact |
|---|---|
| Western US | Wetter, stormier winters |
| Southeast US | Cooler, wetter winters |
| South America (west) | Heavy rain, flooding |
| Australia & Indonesia | Drought, bushfire risk |
| India | Weaker monsoon, less rainfall |
| East Africa | Increased rainfall |
| Northern Europe | Milder winters |
Economic Impact
El Niño affects agriculture, fisheries, and energy worldwide. The 2015-16 El Niño caused an estimated $5.7 billion in damage globally. Peruvian fisheries collapse during strong events as warm water drives away cold-water fish.
How It Is Monitored
Scientists track sea surface temperatures in four Pacific regions (Niño 1+2, 3, 3.4, and 4). An El Niño is declared when the Niño 3.4 region is 0.5°C or more above average for at least five consecutive months.
See how global patterns affect your local weather on Weather Tomorrow.
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