Dr Michael Barnes , ARC Centre of Excellence for the Weather of the 21st Century ( michael . barnes @ monash . edu ) Dr Tess Parker , CSIRO Environment ( tess . parker @ monash . edu ) Dr James Risbey , CSIRO Environment ( james . risbey @ csiro . au )

Northern Australia is one of the wettest parts of the continent . In the dry season , however , typically between April and October , the region receives little to no rainfall . In fact on average , the majority of this region receives less than 10 % of its annual rainfall during August and September . During these two months , this amounts to less than 5 mm for most of the dry region , with only up to 25 mm in parts of the Top End and the Red Centre and up to 50 mm along coastal Queensland and northern New South Wales ( Figure 1 , top panels ).

This year ( 2024 ), however , has been atypical , with several rainfall events impacting the northern parts of the country during August and September . Keen weather-watchers may recall flooding in the Northern Rivers during August and September and images of waterfalls pouring down Uluru during September . The unseasonal rainfall is reflected in the Australian Gridded Climate Data ( AGCD ) rainfall statistics for these two months , provided by the Bureau of Meteorology ( Figure 1 , bottom panels ). This shows vast swaths of the northern parts of Western Australia , the Northern Territory and coastal Queensland receiving abnormal dry-season rainfall .

Although maybe not as spectacular or impactful as a deep extratropical low over the southern states , or a tropical cyclone in the wet season , it is important to understand the dynamics that underpin these kinds of events to give us insight into our current and future climate . Were all these events similar ? How did they unfold ? And can they tell us anything about future dry-season rain over the northern parts of the continent ?

Figure 1 : Top panels : Monthly mean rainfall over Australia for August ( left ) and September ( right ) for the period 1991-2020 . Credit : Bureau of Meteorology . Bottom panels : Percentage of the mean rainfall during August and September 2024 relative to a 1961- 1990 baseline climatology . Credit : Bureau of Meteorology