Statistical analysis of attributions of climatic characteristics to nonstationary rainfall‐streamflow relationship

•Statistical analysis is used to quantify nonstationary rainfall-runoff relationship.•Millennium Drought and pre and post drought data in south-east Australia are used.•Rainy days and wet-spell length can predict streamflow in varied hydroclimates.•Key rainfall characteristics in different periods help explain nonstationarity.•Results explain climate change and variability impacts on regional streamflow.