Pacific Islands Early Action Rainfall Watch : September 2025

Abstract

The El Niño–Southern Oscillation (ENSO) remains neutral. The Indian Ocean Dipole (IOD) index has now met the negative IOD threshold (less than or equal to −0.4 °C) for 7 consecutive weeks. . The Bureau’s model predicts some further cooling of the tropical Pacific is likely, potentially reaching La Niña levels briefly during spring (September to December), and returning to neutral in the austral summer (December to February). This is consistent with most international models assessed, with around half indicating ENSO will remain neutral, and the other half indicating La Niña may develop.