Australia’s Natural Catastrophe Forecast

Australia is about to enter its peak risk period for extreme weather, spanning October to April, when bushfires, cyclones, and floods are most common. The likelihood and intensity of these events are shaped by large-scale climate drivers, most notably the El Niño–Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD). These systems shift between positive, neutral, and negative phases, each defined by sea surface temperature anomalies in the Pacific and Indian Oceans, respectively. 

Currently, both ENSO and the IOD are in negative phases, with forecasts suggesting a gradual return to neutral conditions by February (Southern hemisphere outlooks).  

So, what does that mean for Australia? 

During neutral ENSO and negative IOD conditions, sea surface temperatures northeast and northwest of Australia are anomalously warm, respectively. Air travelling across these regions will heat up, ascend and rain out over Australia. These conditions also favour the formation of tropical cyclones, which can make landfall in Northern Australia. When ENSO enters a negative phase (La Niña), this Pacific circulation pattern strengthens further, amplifying rainfall and cyclone activity. 

Taken together, negative-to-neutral ENSO and IOD conditions significantly raise the likelihood of extreme rainfall across Eastern Australia this summer (Rainfall – The chance of above median for October to December – Climate Outlooks). Historical records reinforce this risk. Since 1967, insured losses from floods and windstorms between October and February align closely with ENSO and IOD phases (Insurance Council of Australia database benchmarked to 2022). While only 49% of years showed both ENSO and IOD values below zero, this subset accounts for 8 of the 10 largest loss years on record. This outlook suggests that wind and rain, rather than bushfires, are the most likely drivers of insured losses this summer.