Corey Robinson, ARC Centre of Excellence for the Weather of the 21st Century( corey. robinson @ monash. edu) Yuxin Wang, Institute for Marine and Antarctic Studies, University of Tasmania, University of Hawaii at Mānoa( yuxinw @ hawaii. edu) Prof Neil Holbrook, Institute for Marine and Antarctic Studies and ARC Centre of Excellence for the Weather of the 21st Century, University of Tasmania, Hobart, Tasmania( neil. holbrook @ utas. edu. au) A / Prof Andrew Dowdy, University of Melbourne( andrew. dowdy @ unimelb. edu. au) Prof Todd Lane, ARC Centre of Excellence for the Weather of the 21st Century( todd. lane @ unimelb. edu. au) Luke Burgess, University of Melbourne( l. burgess1 @ student. unimelb. edu. au)

Australia’ s 2024-2025 summer was the second hottest on record, with temperatures soaring 1.89 ° C above the long-term average.

The unusually hot summer brought its share of climate extremes. Heatwaves affected large parts of the country, torrential rain lashed North Queensland, and an intense marine heatwave off Western Australia likely contributed to mass fish deaths along the Pilbara coast. Meanwhile, bushfires swept through the Grampians National Park, and tropical cyclones Zelia and Sean brought heavy rainfall and destructive winds to parts of Western Australia.

Here, we revisit some of these extraordinary events, explore the conditions that fuelled them, and discuss how such extreme events might evolve in the future.

North Queensland floods

In late January and early February 2025, heavy rainfall hit Northern Queensland, causing significant flooding in Townsville and surrounding regions. The floods claimed at least two lives and caused mass evacuations, power outages and goods shortages in major populated centres.

In early February, some locations along the Townsville-Cairns coastal stretch recorded over 1,000 mm of rainfall in 12 days

( Figure 1). Several locations also broke their rainfall records during the event, including Ingham, which received over 500 mm of rainfall on 3 February.

The extreme rainfall was brought about by a series of weak, slow-moving low-pressure systems near the Queensland coast. Although the systems were barely discernible at the surface and well below tropical cyclone strength, they still produced extreme rainfall, suggesting other factors contributed to the event.

The synoptic chart for 1 February highlights one of these lowpressure systems passing over North Queensland, along with other key contributing factors( Figure 2). Precipitable water— the total amount of moisture from the surface to the top of the atmosphere— was remarkably high near the Townsville coast, with regions above 70 mm. Meanwhile, strong easterly winds associated with a ridge up the east coast of Australia met a stream of warm and humid tropical air from the north associated with the slow-moving low-pressure system( Figure 2). The convergence of these two wind streams, along with abundant moisture, led to large-scale upward motion and the formation of widespread clouds and rainfall. The slow-moving nature of the low-pressure system sustained this rainfall over several days.

Figure 1: Australia Gridded Climate Data( AGCD) accumulated rainfall for 1-12 February. Credit: Bureau of Meteorology

Figure 2: Precipitable water( shaded, mm), 700 hPa geopotential height( black contours), temperature( dashed red contours) and wind barbs for 00 UTC 2 Feb 2025. Source: Alicia Bentley GFS maps