The impacts of extreme precipitation events (EPEs) on society are strongly influenced by their spatial footprint, yet the spatial scales of such events remain underexplored. Here we present the first continent-wide analysis of the spatial scales of daily EPEs in Australia. We estimate the characteristic spatial scale of EPEs seasonally across the Australian continent using daily station observations and semivariograms. A semivariogram is a spatial statistical function that measures how spatial autocorrelation in precipitation decays with distance. Consistent with global analyses of satellite data, EPEs generally have larger spatial scales at higher latitudes. However, our analysis reveals complex seasonal and geographical dependencies that highlight the role of topography and meteorological regimes. We also analyse EPE spatial scales under different phases of the El Niño-Southern Oscillation (ENSO). In SON and DJF, southeastern Australia exhibits larger spatial scales during La Niña, although no uniform pattern is observed across the continent. Long-term changes were analysed using 2,070 stations with continuous operation between 1960 and 2023. Southwestern Australia shows a notable reduction in median EPE length scale in most seasons, while eastern regions exhibit a decrease in MAM and an increase in SON. Together, these findings provide a new climatological reference for the spatial scale of EPEs in Australia. These results also highlight the need to better understand the physical factors controlling the spatial scale of precipitation extremes in current and future climates.
