ENSO-neutral conditions remain in place, and there is a 55% chance that ENSO-neutral conditions will continue during September-November 2025, followed by a 50% chance that ENSO-neutral will remain in place during October- December. However, there is a 40% chance that La Niña will develop by the end of 2025.
As of 18 August 2025, the 30-day NINO3.4 Index (in the central equatorial Pacific) was -0.28˚C, in the neutral range. The 30-day relative Niño 3.4 Index (RONI) was -0.64˚C, reflective of the central equatorial Pacific being cooler than the average of the global tropics and on the La Niña side of neutral.
The Southern Oscillation Index (SOI) was on the La Niña side of the neutral range during June-August (+0.4), while the August value was 0.0 (in the neutral range).
Temperatures in the subsurface equatorial Pacific remain above average in the western part of the basin with cooler than average temperatures developing in the east.
Notably cooler than average temperatures are currently located in the eastern equatorial Pacific at depths of 50-100 metres. Should these cooler water temperatures in the east reach the surface in the coming months, it could push ENSO in a more La Niña direction.
Upper oceanic heat content continues to indicate ENSO neutral conditions.
During September-November, model guidance favours an enhancement in convective forcing over the western Pacific and parts of Melanesia, co-located with the warmest sea surface temperatures. This may lead to enhanced rainfall for island groups such as Palau, western Federated States of Micronesia, and Papua New Guinea east to Fiji and Tonga.
However, drier than normal conditions are increasingly likely to occur for most island groups along and north of the equator, including much of the Marshall Islands, Nauru, Kiribati, Tuvalu, Tokelau, northern Cook Islands, and parts of French Polynesia (see pages 6-7 for more information).
