Seasonal ensemble forecasts for soil moisture, evapotranspiration and runoff across Australia

•We developed a seasonal hydrological ensemble forecasting system for Australia.•The system predicts root-zone soil moisture, evapotranspiration and runoff nationally.•The forecasts use a climate forecasting system combined with a hydrological model.•We assessed the performance of predicting mean conditions and hydrological extremes.•The forecasts show sufficient skill up to three months ahead for many applications.