El Niño & La Niña Tracker
A strong El Niño is developing in the tropical Pacific, with forecasts indicating it could reach a peak of +2.7°C RONI (+3.2°C raw ONI) and potentially exceed the historical record of +2.4°C set in 1982-83…
Summary
A strong is developing in the tropical Pacific, with forecasts indicating it could reach a peak of +2.7°C (+3.2°C raw ) and potentially exceed the historical record of +2.4°C set in 1982-83. Strong events typically alter global weather patterns, driving widespread drought in some regions and heavy rainfall in others. Notably, deep-learning AI forecasts identified this elevated intensity months before traditional physical models adjusted to match it.
Right now
The authoritative Relative () stands at +1.69°C for July-September 2026, establishing a strong state, while legacy reads +2.16°C. Weekly anomalies demonstrate steady intensification, climbing from +2.6°C on 19 August to +3.3°C on 14 October 2026, with sea surface temperatures at 30°C. Atmospheric and oceanic indicators agree strongly: the () reached 2.37, exceeded only 3 times in 120 bi-monthly periods, and the September () registered -2, a low seen only 4 times in 240 months.
Likely impacts
Historical patterns indicate high-confidence global impacts. Maritime Southeast Asia faces an 80% probability of drier conditions during June to December; past very strong events averaged a 41% rainfall deficit in the Philippines during December to February. Coastal Peru and Ecuador have an 80% probability of warmer, wetter conditions in January to March, with Ecuador historically averaging 38% more winter rainfall. Eastern Australia carries a 75% probability of drier, warmer conditions between June and December, where Australia averaged a 25% winter rainfall reduction. Southern Africa has a 70% probability of drier conditions in December to February, with South Africa historically averaging a 33% rainfall drop. East Africa carries a 70% probability of wetter October to December rains, with Kenya historically averaging an 82% winter rainfall surge. Finally, the Southwest United States has a 60% probability of a wetter December to February, where the United States averaged 19% more winter rainfall. The table below shows how this month's readings compare so far.
September 2026's early signs vs. the historically expected signal
Observed = each region’s most direct available signal: a 3-month precipitation anomaly vs. the 1961-1990 baseline where the impact is precipitation-driven, or a temperature departure with its long-term warming trend removed otherwise, so the figure reflects the ENSO signal rather than the global-warming background (the same idea RONI applies to the ocean).
Expected warmer (JFM) · Observed +1.1°C in Peru (trend-removed; raw +2.1°C)
Expected drier (JJA-DJF) · Observed -9% in Indonesia (3mo vs. 1961-90)
Expected drier (JJA-DJF) · Observed +4% in Australia (3mo vs. 1961-90)
Expected drier (JJA-DJF) · Observed -63% in Brazil (3mo vs. 1961-90)
Expected warmer (DJF) · Observed +0.3°C in South Africa (trend-removed; raw +1.3°C)
Expected warmer (DJF) · Observed +1.6°C in Australia (trend-removed; raw +2.1°C)
Expected drier (JJA-OND) · Observed -63% in Brazil (3mo vs. 1961-90)
Expected drier (JJAS) · Observed -14% in India (3mo vs. 1961-90)
Expected cooler (DJF) · Observed +0.7°C in United States (trend-removed; raw +2.5°C)
| Region | Season | Expected | Observed | Verdict |
|---|---|---|---|---|
| Peru & Ecuador (coastal) | JFM | warmer | +1.1°C (Peru, raw +2.1°C) | consistent |
| Maritime SE Asia | JJA-DJF | drier | -9% (Indonesia, 3mo) | consistent |
| Eastern Australia | JJA-DJF | drier | +4% (Australia, 3mo) | inconsistent |
| NE Brazil | JJA-DJF | drier | -63% (Brazil, 3mo) | consistent |
| Southern Africa | DJF | warmer | +0.3°C (South Africa, raw +1.3°C) | consistent |
| Northern Australia | DJF | warmer | +1.6°C (Australia, raw +2.1°C) | consistent |
| Amazon basin | JJA-OND | drier | -63% (Brazil, 3mo) | consistent |
| India | JJAS | drier | -14% (India, 3mo) | consistent |
| Southeast USA | DJF | cooler | +0.7°C (United States, raw +2.5°C) | inconsistent |
How unusual is this
While weekly raw temperatures reached +3.3°C, strength is officially judged using the Relative (), which adjusts for background tropical warming. On the RONI scale, the strongest recorded events are 1982-83 at +2.4°C peak, 1997-98 at +2.28°C, and 2015-16 at +2.25°C. Historical comparisons illustrate the potential scale: the 1982-83 event caused US$13bn in global damage and severe drought in Australia, while the 1997-98 event triggered extensive Indonesian forest fires and East African floods. Forecasters at NOAA's Climate Prediction Center highlight that high raw readings must be distinguished from multi-month RONI metrics when evaluating historical standing.
What's coming
NOAA CPC probabilities assign a 100% chance of a very strong event for September-November and October-December 2026, remaining at 81% for December-February. Official median projections feature two forecast peaks: the NOAA official outlook at +2.7°C RONI (+3.2°C raw ) and the deep-learning SNU CNN model at +2.1°C RONI (+2.5°C raw ONI). The AI model anticipated a strong peak early, whereas traditional physics-based forecasts gradually rose to converge with it. Dynamical model skill at record-challenging extremes remains unproven. A positive typically follows to influence North American winter impacts (extreme weather).
Generated by Gemini from this site's ENSO, temperature and extreme-weather data, and web sources
The El Niño–Southern Oscillation (ENSO) is the single biggest year-to-year driver of global temperature and rainfall after the long-term warming trend itself. It is also a natural amplifier of climate change. During an El Niño, unusually warm water piles up in the eastern tropical Pacific, releasing heat to the atmosphere and lifting global mean temperature by ~0.1–0.3°C for 6–12 months. La Niña does the opposite. ENSO also shifts rainfall and storm tracks worldwide - driving drought in Australia, flooding in Peru, wetter Californias and milder UK winters. Record-warm years almost always coincide with El Niño stacked on top of the long-term warming trend.
ONI stands for Oceanic Niño Index; RONI stands for Relative Oceanic Niño Index, and both measure Sea Surface Temperature (SST) for the Niño 3.4 region - RONI (NOAA’s official index since Feb 2026) subtracts the tropics-wide warming background so strength is judged consistently across the decades.
Current State
Niño 3.4 is the official ENSO yardstick; Niño 1+2 tracks the coast off Peru, Niño 4 the western warm pool.
ENSO state
intensifying100% very strong at peak · Sep-NovWarm Pacific - Global Temperatures Rise
RONI · 3-mo3-month mean
El Niño
+1.7°C
JAS 2026 · ONI +2.2
Niño 3.4 · latest
+3.3°C
SST 30.0°C
w/e 14 Oct 2026
Equatorial Pacific
The red/blue glow shows the latest week’s SST anomaly vs the 1991-2020 baseline. Orange marks the Indo-Pacific Warm Pool, spreading east under El Niño. Arrows show trade-wind direction.
Niño 1+2
+5.2°C
Very strong El Niño-leaning
SST 26.2°C
Niño 3
+4.2°C
Very strong El Niño-leaning
SST 29.2°C
Niño 3.4
+3.3°C
Very strong El Niño-leaning
SST 30.0°C
Niño 4
+1.1°C
Moderate El Niño-leaning
SST 29.7°C
El Niño years push global temperatures higher; La Niña years temporarily damp them - though the underlying greenhouse-gas trend continues either way. Thresholds: ≥ +0.5°C El Niño · ≤ −0.5°C La Niña · otherwise Neutral.
ENSO Forecast
Observed & Forecast
Niño 3.4: solid observed, dashed forecast; teal is raw weekly SST, ~2 months ahead of RONI (shaded gold).
What's Coming
NOAA forecast
Very Strong at peakPeak +2.7/+3.2°C (RONI/ONI median)
El Niño conditions are already in place and forecast to peak at 100% probability in SON-JFM. The dashed off-white curve is NOAA’s own official RONI outlook, peaking in OND 2026. The current forecast was issued October 2026.
SNU AI forecast
Very Strong at peakPeak +2.1/+2.5°C (RONI/ONI)
The dashed purple curve is a deep-learning forecast from Seoul National University, built for predictions up to 18–24 months out. The current forecast was issued October 2026.
Season-by-Season El Niño Probability · Shaded by Strength
Three ENSO indicators on one axis: Niño 3.4 (ocean), MEI v2 (ocean+atmosphere) and −SOI (sign-flipped so all three rise together for El Niño). When all three climb past +0.5, the forecast has independent support.
Indicators: NOAA CPC Niño-region SSTs, NOAA PSL MEI v2, NOAA CPC SOI.
Sources: NOAA CPC weekly Niño 3.4 SST (observed), NOAA official RONI outlook and NOAA CPC probability outlook (forecast), NOAA RONI (legacy ONI v5 kept for continuity), and NOAA CPC strength outlook, and SNU ACE Lab CNN forecast (Ham et al. 2019, Nature). RONI methodology: Stockdale (2026, ECMWF). Raw model forecasts are converted to RONI using the observed seasonal ONI−RONI gap (currently ~+0.4–0.5°C).
ENSO's Partners
Indian Ocean Dipole (IOD)
ENSO's Indo-Pacific partner: El Niño usually brings a positive IOD, La Niña a negative one.
Indian Ocean Dipole now
Positive IOD
Dipole Mode Index +0.88°C · week to 2026-10-18 (BOM)
Indian Ocean DipoleENSO and the IOD right now
Positive IOD is currently reinforcing El Niño - the classic co-occurring pairing, which typically means an even sharper east/west rainfall contrast around the Indian Ocean than either driver alone.
ENSO and the IOD - a pair that often work together
- The Pacific usually leads. El Niño mostly comes with a positive IOD and La Niña with a negative one - the IOD often starts in spring as ENSO develops and peaks in late autumn.
- The Indian Ocean feeds back. A strong IOD can reinforce the ENSO event it grows alongside, and a positive IOD tends to set up La Niña the following year (a negative one, El Niño).
- The link is getting stronger. Coupling between the two oceans has strengthened since the 1980s - enough to account for up to a fifth of the recent increase in ENSO’s swings.
- Each can act alone. The IOD can develop without ENSO, and the pairing isn’t guaranteed in any one event.
Pacific-North American Pattern (PNA)
ENSO's route into North American weather: a pressure pattern from near Hawaii to North America that El Niño tilts positive and La Niña negative, mainly in winter.
PNA - today
-0.19
Neutral · 2026-10-19
30-day rolling mean
last monthly -0.64 · 2026-09
Last sign flip
-
no recent sustained flip
ENSO and the PNA right now
El Niño is active, but the PNA's link to ENSO is a cold-season effect - expect it to show from late autumn, through to March.
The PNA - ENSO’s route into North American weather
- El Niño tilts it positive. In 19 of the 26 El Niño winters since 1951, the December-February PNA was positive.
- La Niña’s pull is weaker. Only 13 of 24 La Niña winters had a negative PNA.
- What a positive PNA brings. Milder western Canada and far-western US; cooler south-central and south-eastern US; wetter Gulf of Alaska and Pacific Northwest; drier upper Midwest. A negative PNA roughly reverses this.
- It is mostly its own pattern. The PNA is a natural mode of the atmosphere that ENSO only tilts - ENSO explains about 10% of its winter ups and downs, and it has little effect on North American temperatures in summer.
Sources: NOAA CPC - Pacific/North American pattern; Straus & Shukla (2002), Does ENSO Force the PNA?; winter counts from this site’s NOAA CPC PNA and RONI series.
+PNA (the El-Niño-favoured phase) means higher pressure near Hawaii and over the western interior of North America, and lower pressure south of the Aleutians and over the south-eastern US. -PNA (La-Niña-favoured) is the reverse. Data: NOAA CPC daily PNA.
Strongest Events
Strongest ENSO Events
The top 6 since 1950 by peak RONI.
El Niño
La Niña
Bars = peak RONI per episode; (raw x) = un-adjusted Niño 3.4 SST.
Global Impact Tracker
ENSO's Global Footprint
How each country's temperature or rainfall departed from its 1961-1990 baseline in past ENSO events - scrub the timeline to step through them.
Loading impact map…
Past Events
What Happened Last Time?
The 15 most consequential ENSO events since 1950; bar height is peak RONI.
2023-2024 El Niño
strong +1.5/+2.0°C (RONI/ONI)Peaked DJF 2023-24. Combined with the long-term warming trend, helped make 2023 and then 2024 the two hottest years on record by clear margins.
- 2024: first calendar year >1.5 °C above pre-industrial (Copernicus)
- Record Amazon drought (lowest Rio Negro at Manaus)
- Mediterranean & North Atlantic marine heatwaves
- Global mass coral bleaching #4 (declared April 2024)
Most reliable footprint: Suriname ran +1.5°C that winter - ENSO alone explains ~55% of its year-to-year swing; Venezuela and Bolivia moved almost as tightly with it.
2020-2023 La Niña
strong -1.5/-1.3°C (RONI/ONI)A rare triple-dip La Niña (3 successive winters). Cumulative impacts much larger than any single winter would suggest.
- Horn of Africa drought - worst in 40 years (~20M food-insecure)
- Hyperactive 2020 Atlantic hurricane season (30 named storms)
- 2022 Pakistan floods (~33M affected, ~8M displaced)
- Reinforced US SW megadrought
Most reliable footprint: Botswana ran -1.6°C in the first of its three winters - ENSO alone explains ~44% of its year-to-year swing, holding up consistently across this rare triple-dip event.
2014-2016 El Niño
very strong +2.4/+2.8°C (RONI/ONI)A "Godzilla" El Niño - peak RONI on par with 1997-98. Pushed global temperature ~0.2 °C above the long-term trend at peak.
- 2015 & 2016 set successive global temperature records
- Ethiopia & Southern Africa drought (~60M people food-insecure)
- Indonesia fires (worst since 1997)
- Global mass coral bleaching #3 (2014-17)
Most reliable footprint: Botswana ran +0.9°C that winter - ENSO alone explains ~44% of its year-to-year swing. This "Godzilla" event’s headline record warmth was global and trend-driven; the reliably ENSO-attributable part of its footprint was smaller and concentrated in the tropics/southern Africa.
2010-2011 La Niña
strong -1.7/-1.6°C (RONI/ONI)Co-incident with the strongest negative Southern Oscillation Index since 1917. Drove some of the most extreme rainfall events on record.
- QLD & Brisbane floods (Jan 2011)
- Pakistan floods (mid-2010, 20M affected)
- 2010 Russian heatwave (linked indirectly)
- Horn of Africa drought (2010-12)
Most reliable footprint: Namibia ran -1.1°C that winter - ENSO alone explains ~48% of its year-to-year swing. The 2010 Russian heatwave above is the opposite kind of story: real, but driven mostly by blocking, not ENSO - Russia’s own ENSO link tests at close to zero in this dataset.
2007-2008 La Niña
strong -1.6/-1.6°C (RONI/ONI)A strong, fast-developing La Niña that made 2008 the coolest year of its decade - while still leaving it warmer than almost every year of the 20th century, an early lesson in how the warming trend rides through the cycle.
- Two Category 5 Atlantic hurricane landfalls in 2007 (Dean, Felix)
- Deepened the US Southeast drought; record 2008 US Midwest floods
- Sharpened the 2007-08 global food price stress
Most reliable footprint: Botswana ran -1.5°C that winter - ENSO alone explains ~44% of its year-to-year swing.
1998-2001 La Niña
strong -1.7/-1.7°C (RONI/ONI)A multi-year ("triple-dip-style") La Niña following the 1997-98 El Niño. Hyperactive Atlantic hurricane seasons.
- 1998 Hurricane Mitch (~11,000 dead in C. America)
- Sahel & Horn-of-Africa drought
- Strong Indian monsoon years
Most reliable footprint: Zimbabwe ran -1.3°C that winter - ENSO alone explains ~45% of its year-to-year swing.
1997-1998 El Niño
very strong +2.4/+2.4°C (RONI/ONI)One of the most extreme El Niños of the 20th century. Briefly pushed global temperatures to a new record and caused widespread climate dislocation.
- Indonesian peatland fires & haze (~1Gt CO₂ emitted)
- East African short-rains floods (millions displaced)
- California floods & ice storms in NE US/Canada
- Coral bleaching across the Indo-Pacific
Most reliable footprint: Costa Rica ran +1.0°C that winter - ENSO alone explains ~82% of its year-to-year swing, the strongest single-country link in this entire dataset.
1991-1992 El Niño
very strong +2.3/+1.7°C (RONI/ONI)A strong El Niño by the raw index, but Mount Pinatubo’s 1991 eruption cooled the wider tropics - so on the warming-adjusted RONI scale it ranks very strong, since RONI measures Niño 3.4 against that cooler tropical background. In southern Africa it drove the region’s worst drought of the 20th century.
- Southern Africa’s 1991-92 drought - harvests halved, tens of millions needing food aid
- US West Coast storms and Texas floods
- Global temperature signal muted by Pinatubo
Most reliable footprint: Zimbabwe ran +1.8°C that winter - ENSO alone explains ~45% of its year-to-year swing, consistent with the drought this event is remembered for.
1988-1989 La Niña
strong -1.9/-1.9°C (RONI/ONI)Strong La Niña following the 1986-87 El Niño. Reinforced the 1988 US Midwest drought and helped seed an active North Atlantic hurricane season.
- 1988 US Midwest drought (US$80bn+ damages)
- Severe Sudan/Bangladesh floods
- Strong Indian monsoon recovery
Most reliable footprint: Botswana ran -2.2°C that winter - ENSO alone explains ~44% of its year-to-year swing, one of the sharpest La Niña cold snaps in the record.
1982-1983 El Niño
very strong +2.5/+2.2°C (RONI/ONI)A textbook East-Pacific El Niño that arrived almost without forecast. Caused the largest ENSO-related humanitarian crisis to that date.
- Severe Australian drought (one of worst on record)
- Indonesian forest fires & food shortages
- Catastrophic floods Peru/Ecuador
- US$13bn (1983 USD) damage worldwide
Most reliable footprint: Zimbabwe ran +2.0°C that winter - ENSO alone explains ~45% of its swing; Peru (+1.1°C) tracked even more consistently, at ~76%.
1973-1976 La Niña
strong -1.9/-2.0°C (RONI/ONI)A deep multi-year La Niña that swung straight out of the 1972-73 El Niño - one of the strongest cold events in the modern record. Its imprint marks the last time the yearly global temperature dipped close to the 20th-century average.
- Australia’s wettest year on record (1974), including Brisbane’s January flood
- Catastrophic 1974 Bangladesh monsoon floods
- Pronounced global cool dip through 1974-76
Most reliable footprint: Botswana ran -2.0°C that winter - ENSO alone explains ~44% of its year-to-year swing.
1972-1973 El Niño
very strong +2.3/+2.1°C (RONI/ONI)Arguably the most economically consequential El Niño ever. It collapsed Peru’s anchoveta fishery, then the largest fishery on Earth, and the shock cascaded through global fishmeal, soy and grain prices in an already tight world food market.
- Peruvian anchoveta catch crashed from ~12M to ~2M tonnes and never fully recovered
- Amplified the 1972-74 global food price crisis
- Drought in the Sahel, India and Australia; floods in coastal Peru
Most reliable footprint: Botswana ran +2.6°C that winter - ENSO alone explains ~44% of its year-to-year swing, one of the biggest reliably-ENSO-linked swings on record.
1965-1966 El Niño
very strong +2.0/+2.0°C (RONI/ONI)A powerful event that landed during India’s back-to-back 1965-66 monsoon failures, deepening a food crisis that pushed India into dependence on emergency grain shipments and helped trigger the Green Revolution.
- Indian monsoon failure and food crisis (the “ship-to-mouth” years)
- Drought across Indonesia and parts of Australia
- Falling anchoveta catches off Peru - an early warning before 1972
Most reliable footprint: Suriname ran +1.3°C that winter - ENSO alone explains ~55% of its year-to-year swing.
1957-1958 El Niño
very strong +2.0/+1.8°C (RONI/ONI)The first El Niño observed in scientific detail, coinciding with the International Geophysical Year measurement campaign. The data it produced seeded Bjerknes’ theory of the coupled ocean-atmosphere cycle that underpins ENSO science today.
- First event tracked by a worldwide observing network (IGY 1957-58)
- Marked North Pacific warmth and a poor Peruvian fishing season
- Weakened Indian monsoon and regional crop stress
Most reliable footprint: Panama ran +1.0°C that winter - ENSO alone explains ~79% of its year-to-year swing, one of the strongest single-country links anywhere in this dataset.
1954-1956 La Niña
strong -1.6/-1.7°C (RONI/ONI)A persistent multi-year La Niña through the mid-1950s, one of the longest cold spells on record. Remembered for hemisphere-wide drought and an exceptionally destructive stretch of Atlantic hurricanes.
- Multi-year drought across the US Southwest and southern Plains
- Destructive 1954-55 Atlantic hurricanes (Hazel, Connie, Diane)
- Deep cold anomalies across the eastern Pacific for nearly three years
Most reliable footprint: Botswana ran -1.5°C that winter - ENSO alone explains ~44% of its year-to-year swing, among the strongest links in this dataset.
Source: NOAA RONI (peak RONI + classification) and legacy ONI v5 (shown for context); country footprint figures from the same ENSO-attribution analysis used in the map above (Copernicus ERA5, GPCC/DWD precipitation, NOAA CPC).
ENSO-Driven Countries
How Much ENSO Drives Each Country
How much of each place’s winter (DJF) temperature or rainfall swing ENSO’s phase explains, 1950-2025 - near the top, El Niño or La Niña largely decide the winter.
Most ENSO-Driven
ENSO explains most of the swingLeast ENSO-Driven
Mostly other weather, not ENSOBy Continent
Mean of each continent's countriesSouth America
North America
Africa
Oceania
Asia
Europe
World Impacts
Typical Weather
Each region's usual response to each phase, and how often it happens when that phase is active.
Peru & Ecuador (coastal)
JFMS. America · Western coast of equatorial S. America
Severe coastal flooding, fisheries collapse (anchovy stocks crash as upwelling weakens). 1982-83 and 1997-98 events caused widespread infrastructure damage.
NE Brazil
JJA-DJFS. America · Sertão & northeastern coast
Major drought risk during the rainy season (Feb-May). Severe in 2015-16; agricultural and water-supply crises.
S. Brazil, Uruguay & N. Argentina
NDJS. America · La Plata basin
Wetter-than-average spring/summer; flooding along the Paraná/Uruguay rivers (e.g. 1997-98 floods).
Amazon basin
JJA-ONDS. America · Northern & central Amazonia
Drought stress, lower river levels, larger fire seasons. 2023-24 El Niño produced record-low Rio Negro levels at Manaus.
Southwest USA
DJFN. America · California, Arizona, NM, S. Nevada
Wetter winter; helps replenish reservoirs and snowpack. Strong El Niños have produced major California floods.
Pacific NW USA & W. Canada
DJFN. America · Washington, Oregon, BC, Alberta
Mild, dry winter; lower mountain snowpack. Knock-on summer wildfire risk.
Southeast USA
DJFN. America · Florida & Gulf Coast states
Wetter, cooler winter; stronger subtropical jet brings more storms.
NE USA & E. Canada
DJFN. America · Northeast US states & Maritime Canada
Milder-than-average winter; reduced heating demand.
Mexico & Central America
JJA-SONC. America · From northern Mexico to Panama
Drought risk during the rainy season (May-Oct); crop and water-supply stress, especially in the Central American Dry Corridor.
Caribbean & Atlantic basin
JJA-SONC. America · Caribbean Sea, Gulf of Mexico, tropical Atlantic
Suppresses Atlantic hurricane activity (more wind shear, drier mid-troposphere).
N. Europe (Baltic & UK)
DJFEurope · British Isles, Scandinavia, Baltic
Tendency for cooler late winters; very strong El Niños (1997-98, 1982-83) flipped the sign and gave warm winters.
East Africa (Horn)
ONDAfrica · Kenya, Somalia, Tanzania, Uganda
"Short rains" (Oct-Dec) much wetter; flooding & locust outbreaks. 1997-98 floods displaced millions.
Southern Africa
DJFAfrica · S. Africa, Zimbabwe, Mozambique, Botswana
Major maize-belt drought; 2015-16 El Niño caused the worst SADC drought in decades. 2023-24 again triggered widespread food insecurity.
Sahel
JASAfrica · From Senegal east to Sudan
Drier West African monsoon; reduced cereal yields.
India
JJASAsia · Indian subcontinent
Weaker SW summer monsoon; ~60 % of all-India droughts since 1900 occurred in El Niño years (e.g. 2002, 2009, 2015).
Maritime SE Asia
JJA-DJFAsia · Indonesia, Malaysia, Philippines, PNG
Severe drought; major peatland & forest fires (Indonesia 1997, 2015). One of the most reliable ENSO teleconnections worldwide.
E. Asia (China, Korea, Japan)
DJFAsia · NE China, Korea, Japan
Mild winter; increased rainfall over central/E China (Yangtze flooding risk in following summer).
Eastern Australia
JJA-DJFOceania · NSW, Queensland, Victoria
Drought, heatwaves and severe bushfire seasons. Black Summer (2019-20) ran on a positive Indian Ocean Dipole + weak El Niño.
Northern Australia
DJFOceania · Top End, Cape York
Late, weaker monsoon; drought risk for cattle stations.
Central Tropical Pacific Is.
DJFPacific Is. · Kiribati, Tuvalu, Tokelau, etc.
Migration of the rain belt eastwards; severe coral bleaching during strong events (1998, 2016, 2024).
SW Pacific (Fiji, Vanuatu, NC)
DJFPacific Is. · Fiji, Vanuatu, Samoa, New Caledonia
Drought and a late start to the wet season, with drier, cooler dry seasons (PCCSP); tropical cyclones shift further east toward French Polynesia.
Sources: Met Office GPC ENSO impacts maps (Davey et al. 2013); NOAA CPC ENSO composites and historical analyses; IPCC AR6 WGI Annex VI (ENSO regional teleconnections); Pacific Climate Change Science Program country reports; Mariotti et al. (2002).
ENSO and Climate Change
Is Warming Changing ENSO?
ENSO is a natural cycle thousands of years old; warming now adds to every El Niño, sharpening droughts, floods, heatwaves and record global heat.
Intensification of Extremes
ENSO is a natural cycle, but climate change acts as a force multiplier. Higher global temperatures are deepening El Niño droughts in Australia, Brazil and the Amazon, and driving heavier rainfall across the southern US and East Africa - the same teleconnection patterns, but with sharper edges.
More Frequent, More Intense Events
Warmer sea-surface temperatures favour more rapid ENSO development and a higher occurrence of strong El Niño events. IPCC AR6 (2021) found with high confidence that ENSO SST variability over the past 50 years has been larger than at any time in the previous 400.
Temperature Records Stack Up
Every El Niño now releases its heat onto a baseline already ~1.3°C above pre-industrial. The 1997-98, 2015-16 and 2023-24 events each set new global temperature records; 2024 became the first calendar year above 1.5°C. Without continued greenhouse-gas warming the same ENSO events would have produced much smaller spikes.
La Niña No Longer Cools Below the Trend
Strong La Niña years used to deliver global mean temperatures below the long-term average. Today, even the deepest La Niñas (2020-22) sit well above any 20th-century year. La Niña now buys a temporary pause in record-breaking - it does not reverse the warming.
Oceans and Sea Ice Take a Hit
Warmer ocean waters combined with ENSO trigger more widespread coral bleaching and deeper marine heatwaves. The atmospheric changes also push warmer water to higher latitudes, helping to reduce Arctic sea ice during strong El Niño years.
Coral Bleaching TrackerA More Volatile Climate System
An accelerated Hadley circulation during El Niño, combined with a warmer atmosphere holding ~7% more moisture per °C, is making compound extremes harder to predict. Most CMIP6 models project ENSO rainfall variability will increase with further warming - bigger droughts and bigger floods in the same teleconnection regions.
Sources: IPCC AR6 WGI Chapter 4, Box TS.13; Grothe et al. 2020 (coral records of ENSO amplification); Cai et al. 2021 (Nature Climate Change).
Explore
Related Dashboards
Data Sources
Methodology & Sources
- Oceanic Niño Index (ONI) - 3-month running mean of ERSSTv5 SST anomalies in the Niño 3.4 box (5°S–5°N, 170°W–120°W) relative to a centred 30-year base period that updates every 5 years. NOAA's official ENSO yardstick.
- Relative Oceanic Niño Index (RONI) - NOAA's official ENSO index since Feb 2026, and the single classification/record/forecast basis used throughout this site. RONI scales the raw Niño 3.4 anomaly by a monthly factor (~1.1 in Jul–Aug to ~1.4 in Mar–Apr) after subtracting the tropical-mean (20°N–20°S) SST anomaly, so a warming background ocean does not by itself inflate ENSO strength. Raw ONI is retained alongside RONI as a secondary figure. Stockdale (2026, ECMWF Science Blog).
- Weekly Niño-region SSTs - OISSTv2-based weekly mean SST and SST anomaly (1991–2020 baseline) for Niño 1+2, 3, 3.4 and 4.
- Multivariate ENSO Index v2 - bi-monthly principal- component combination of SST, sea-level pressure, zonal & meridional surface winds and outgoing longwave radiation over the tropical Pacific. Captures atmospheric coupling.
- Southern Oscillation Index - standardised difference in sea-level pressure between Tahiti and Darwin. The classical atmospheric measure of ENSO; persistent negative SOI accompanies El Niño.
- NOAA CPC strength probabilities - monthly official odds of each strength category (weak / moderate / strong / very strong per phase) using RONI thresholds. Shown as shading in the season-by-season probability bars.
- AI briefing - generated by Gemini, grounded in this page's own data plus a curated regional impact matrix (Met Office GPC / Davey et al. 2013 / NOAA composites), documented consequences of comparable past events, this month's country-level temperature anomalies, and active extreme weather (GDACS) - with search grounding for recent expert commentary. The "early signs" table beneath the briefing - comparing each named region's current temperature anomaly against its historically expected signal - is computed entirely in code, not by the AI: it's handed a finished fact, not asked to work it out. Cached and regenerated when new weekly observations or a new monthly forecast issuance arrive.
Snapshot generated Thu, 22 Oct 2026 04:23:35 GMT. Refreshed monthly.