The three strongest El Ninos since 1950 by ONI peaked at about +2.1 °C (1982-83), +2.4 °C (1997-98) and +2.6 °C (2015-16). 2023-24 peaked at about +2.0 °C.
El Nino basics
The Overview page compares the current event with these past events. Values below are the peak 3-month ONI and RONI from the NOAA CPC data files (downloaded 2026-09-24). ONI and RONI differ because RONI removes the warming of the whole tropics (see RONI (Relative Oceanic Nino Index)).
Notes:
1982-83: one of the strongest on record; it was not predicted in advance.
1997-98: one of the strongest; TMD notes it developed fast and brought drought to Thailand and fires in Indonesia and Malaysia (haze).
2015-16: the highest ONI peak in the record; severe drought in Thailand and haze across the region.
2023-24: strong by ONI (about +2.0) but only moderate by RONI (+1.4), because the whole tropical ocean was unusually warm at the time. This is exactly why NOAA moved to RONI.
Thresholds
Event
Peak ONI (season)
Peak RONI (season)
1982-83
+2.14 (DJF 1983)
+2.40 (DJF 1983)
1997-98
+2.37 (NDJ 1997)
+2.28 (NDJ 1997)
2015-16
+2.59 (NDJ 2015)
+2.25 (NDJ 2015)
2023-24
+1.99 (NDJ 2023)
+1.42 (OND 2023)
Source: cpc.ncep.noaa.gov/data/indices/oni.ascii.txt and RONI.ascii.txt. Recent values can be revised for up to two months.