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HOME > Climate & Weather Linkage > El Niño / Southern Oscillation (ENSO) > Relative Oceanic Niño Index (RONI): Historical El Niño / La Niña episodes (1950–Present)

Cold & Warm Episodes by Season

Relative Oceanic Niño Index (RONI):
Historical El Niño / La Niña episodes (1950–Present)

Warm (red) and cold (blue) periods based on a threshold of +/- 0.5°C for the Relative Oceanic Niño Index (RONI), using the 1991–2020 base period [3 month running mean of ERSST.v5 SST anomalies in the Niño 3.4 region (5°N–5°S, 120°–170°W) with average tropical mean (20°N–20°S) SST anomalies subtracted. The difference is then adjusted so the variance equals the original Niño 3.4 index].

For historical purposes, periods of below and above normal SSTs are colored in blue and red when the threshold is met for a minimum of five (5) consecutive overlapping seasons. The RONI is one measure of the El Niño Southern Oscillation, and other indices can confirm whether features consistent with a coupled ocean-atmosphere phenomenon accompanied these periods.

Warm value: The three month running average where the Relative Oceanic Niño Index (RONI) is greater than 0.5 degrees Celsius (El Niño).

Cold value: The three month running average where the Relative Oceanic Niño Index (RONI) is less than -0.5 degrees Celsius (La Niña).

Data availability: 1950–2025

Notice: This page is updated by the 5th of each month. Because of the high frequency filter applied to the ERSSTv5 data (Huang et al. 2017, J. Climate), RONI values may change up to two months after the initial "real time" value is posted. Therefore, the most recent RONI values should be considered an estimate.

View the Oceanic Niño Index (ONI)
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Relative Oceanic Niño Index (RONI): The three month running average of the relative Niño 3.4 index

Year The year

 DJF Dec Jan Feb JFM Jan Feb Mar FMA Feb Mar Apr MAM Mar Apr May AMJ Apr May Jun MJJ May Jun Jul JJA Jun Jul Aug JAS Jul Aug Sep ASO Aug Sep Oct SON Sep Oct Nov OND Oct Nov Dec NDJ Nov Dec Jan

1950

-1.5-1.3-1.1-1.1-1.0-0.7-0.4-0.2-0.2-0.3-0.4-0.6

1951

-0.5-0.20.30.60.60.70.70.80.91.00.90.8

1952

0.60.40.40.40.30.10.00.00.10.00.00.2

1953

0.50.80.80.80.80.80.70.70.70.80.80.9

1954

1.00.70.1-0.2-0.3-0.3-0.5-0.7-0.8-0.7-0.6-0.4

1955

-0.4-0.3-0.3-0.4-0.4-0.4-0.4-0.6-1.0-1.4-1.6-1.3

1956

-0.7-0.3-0.2-0.10.0-0.1-0.3-0.3-0.3-0.3-0.4-0.2

1957

0.00.40.71.01.11.21.21.31.21.31.51.9

1958

2.01.91.41.10.80.70.50.30.20.30.40.7

1959

0.80.80.70.40.3-0.1-0.2-0.4-0.3-0.3-0.10.0

Year The year

 DJF Dec Jan Feb JFM Jan Feb Mar FMA Feb Mar Apr MAM Mar Apr May AMJ Apr May Jun MJJ May Jun Jul JJA Jun Jul Aug JAS Jul Aug Sep ASO Aug Sep Oct SON Sep Oct Nov OND Oct Nov Dec NDJ Nov Dec Jan

1960

0.00.00.00.10.10.00.10.20.20.10.00.0

1961

0.10.10.00.10.30.30.2-0.1-0.3-0.3-0.2-0.1

1962

-0.1-0.1-0.1-0.2-0.3-0.2-0.1-0.2-0.2-0.4-0.5-0.5

1963

-0.4-0.10.20.20.20.40.71.01.01.11.21.3

1964

1.10.70.1-0.4-0.6-0.6-0.6-0.6-0.7-0.8-0.7-0.5

1965

-0.20.10.20.40.61.01.41.71.92.02.01.9

1966

1.71.51.30.90.50.30.30.10.0-0.1-0.1-0.2

1967

-0.2-0.2-0.4-0.4-0.20.20.30.10.0-0.10.00.0

1968

-0.2-0.3-0.3-0.20.20.50.70.60.50.60.81.1

1969

1.21.10.90.50.40.20.20.40.70.80.70.6

Year The year

 DJF Dec Jan Feb JFM Jan Feb Mar FMA Feb Mar Apr MAM Mar Apr May AMJ Apr May Jun MJJ May Jun Jul JJA Jun Jul Aug JAS Jul Aug Sep ASO Aug Sep Oct SON Sep Oct Nov OND Oct Nov Dec NDJ Nov Dec Jan

1970

0.50.30.30.10.0-0.3-0.6-0.7-0.7-0.6-0.7-0.9

1971

-1.0-1.0-0.8-0.6-0.5-0.4-0.4-0.4-0.5-0.5-0.5-0.5

1972

-0.30.00.40.80.91.11.31.51.72.02.22.3

1973

2.01.40.6-0.2-0.8-1.1-1.2-1.4-1.5-1.8-1.9-1.9

1974

-1.5-1.2-0.9-0.9-0.8-0.6-0.4-0.2-0.2-0.4-0.4-0.2

1975

-0.1-0.1-0.3-0.5-0.6-0.8-0.9-0.9-1.0-1.0-1.1-1.1

1976

-1.0-0.6-0.3-0.10.00.20.50.70.91.11.11.1

1977

1.00.90.50.30.20.40.40.60.81.01.11.1

1978

0.90.60.1-0.2-0.4-0.3-0.3-0.3-0.20.00.20.2

1979

0.20.20.20.20.1-0.10.00.20.40.50.50.7

Year The year

 DJF Dec Jan Feb JFM Jan Feb Mar FMA Feb Mar Apr MAM Mar Apr May AMJ Apr May Jun MJJ May Jun Jul JJA Jun Jul Aug JAS Jul Aug Sep ASO Aug Sep Oct SON Sep Oct Nov OND Oct Nov Dec NDJ Nov Dec Jan

1980

0.60.50.30.20.30.30.20.00.00.10.20.2

1981

0.0-0.3-0.3-0.3-0.3-0.3-0.3-0.2-0.1-0.2-0.20.0

1982

0.10.30.40.60.80.80.91.31.82.22.42.5

1983

2.52.21.71.41.00.60.1-0.2-0.6-0.9-1.1-1.0

1984

-0.5-0.3-0.3-0.5-0.6-0.4-0.2-0.1-0.1-0.5-0.8-1.0

1985

-0.8-0.6-0.6-0.7-0.7-0.5-0.4-0.3-0.2-0.2-0.1-0.2

1986

-0.3-0.3-0.2-0.1-0.1-0.10.30.60.91.21.41.5

1987

1.61.51.31.00.91.11.31.61.51.31.00.9

1988

0.70.3-0.2-0.7-1.4-1.7-1.6-1.3-1.4-1.6-1.9-1.9

1989

-1.7-1.4-1.1-0.8-0.6-0.4-0.3-0.3-0.2-0.2-0.10.0

Year The year

 DJF Dec Jan Feb JFM Jan Feb Mar FMA Feb Mar Apr MAM Mar Apr May AMJ Apr May Jun MJJ May Jun Jul JJA Jun Jul Aug JAS Jul Aug Sep ASO Aug Sep Oct SON Sep Oct Nov OND Oct Nov Dec NDJ Nov Dec Jan

1990

0.20.30.30.30.20.20.30.40.40.40.40.5

1991

0.60.50.40.40.50.70.80.80.91.21.72.1

1992

2.32.22.01.71.40.90.50.30.20.10.10.3

1993

0.50.70.91.00.90.70.50.50.50.40.30.3

1994

0.30.30.40.50.60.60.70.81.01.11.31.4

1995

1.31.00.70.40.1-0.1-0.3-0.5-0.7-0.9-0.9-0.9

1996

-0.9-0.8-0.6-0.4-0.3-0.3-0.2-0.2-0.2-0.3-0.3-0.3

1997

-0.2-0.10.20.51.01.31.72.02.32.42.42.3

1998

2.21.81.30.80.1-0.5-1.2-1.4-1.5-1.5-1.6-1.6

1999

-1.5-1.3-1.1-1.0-1.0-1.0-1.0-1.0-1.0-1.1-1.4-1.6

Year The year

 DJF Dec Jan Feb JFM Jan Feb Mar FMA Feb Mar Apr MAM Mar Apr May AMJ Apr May Jun MJJ May Jun Jul JJA Jun Jul Aug JAS Jul Aug Sep ASO Aug Sep Oct SON Sep Oct Nov OND Oct Nov Dec NDJ Nov Dec Jan

2000

-1.7-1.4-1.1-0.8-0.6-0.5-0.4-0.4-0.4-0.6-0.7-0.7

2001

-0.6-0.5-0.5-0.5-0.3-0.10.00.00.0-0.2-0.2-0.3

2002

-0.10.00.00.10.40.70.91.11.31.41.51.2

2003

0.90.50.2-0.2-0.4-0.30.00.20.20.20.30.3

2004

0.30.10.10.20.30.50.70.80.90.80.70.7

2005

0.60.40.30.30.20.0-0.1-0.10.0-0.2-0.5-0.8

2006

-0.9-0.9-0.6-0.4-0.10.00.10.30.50.80.90.9

2007

0.60.2-0.2-0.4-0.4-0.5-0.6-0.8-1.0-1.3-1.4-1.5

2008

-1.6-1.5-1.3-0.9-0.8-0.5-0.3-0.2-0.3-0.4-0.6-0.8

2009

-0.9-0.8-0.7-0.4-0.10.10.30.40.60.91.31.6

Year The year

 DJF Dec Jan Feb JFM Jan Feb Mar FMA Feb Mar Apr MAM Mar Apr May AMJ Apr May Jun MJJ May Jun Jul JJA Jun Jul Aug JAS Jul Aug Sep ASO Aug Sep Oct SON Sep Oct Nov OND Oct Nov Dec NDJ Nov Dec Jan

2010

1.51.10.60.1-0.5-1.0-1.3-1.5-1.7-1.7-1.7-1.6

2011

-1.4-1.2-0.9-0.7-0.5-0.3-0.4-0.5-0.7-0.9-1.0-1.0

2012

-0.8-0.6-0.6-0.5-0.30.00.30.40.40.2-0.1-0.4

2013

-0.6-0.6-0.5-0.4-0.4-0.4-0.4-0.3-0.3-0.2-0.2-0.3

2014

-0.5-0.5-0.30.00.10.0-0.1-0.10.10.40.50.6

2015

0.50.40.50.60.81.01.31.61.92.22.32.4

2016

2.21.81.30.5-0.1-0.6-0.9-1.0-1.1-1.1-1.1-1.0

2017

-0.7-0.5-0.3-0.10.10.1-0.2-0.5-0.7-1.0-1.1-1.3

2018

-1.1-1.0-0.9-0.7-0.30.00.10.20.40.70.80.7

2019

0.60.60.60.50.30.20.0-0.10.00.10.20.2

Year The year

 DJF Dec Jan Feb JFM Jan Feb Mar FMA Feb Mar Apr MAM Mar Apr May AMJ Apr May Jun MJJ May Jun Jul JJA Jun Jul Aug JAS Jul Aug Sep ASO Aug Sep Oct SON Sep Oct Nov OND Oct Nov Dec NDJ Nov Dec Jan

2020

0.10.10.0-0.3-0.6-0.8-0.8-0.9-1.2-1.5-1.5-1.4

2021

-1.2-1.0-1.0-0.8-0.6-0.5-0.6-0.7-0.9-1.1-1.2-1.2

2022

-1.2-1.2-1.3-1.3-1.2-1.0-0.9-1.0-1.1-1.1-1.0-1.0

2023

-0.8-0.6-0.4-0.20.10.40.60.91.11.41.51.5

2024

1.20.90.50.1-0.3-0.5-0.5-0.6-0.8-0.8-0.9-1.1

2025

-1.1-0.9-0.7-0.5-0.5-0.4-0.5-0.6-0.8-0.9-0.9-1.0
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