Abstract Forecasting river ice breakup is critical for supporting emergency responses to river ice-related flooding along rivers in the northern hemisphere. However, due to complex river ice processes, forecasting river ice breakup is more challenging than predicting open-water flood conditions. Although considerable progress has been made in understanding the mechanisms and characteristics of breakup processes and in forecasting breakup timing using empirical methods at the local scale, fewer advances have been made in understanding and forecasting breakup using physically-based models, particularly at the catchment scale. In this study, we present a physically-based coupled hydrological and water temperature modelling framework for breakup prediction in cold region catchments in real time. The modelling framework was applied for operational forecasting of the 2019 breakup event along the Athabasca River at Fort McMurray in Alberta. Further model validation was performed by hindcasting the 2016, 2017 and 2018 breakup events. The model shows promising results for predicting the ice cover breakup with an average error of about 5 days, demonstrating its usefulness in real-time operational forecasting. Importantly, the model generates breakup progression at the catchment scale, providing an advantage over existing site specific breakup prediction methods.