Owing to the massive tidal range, available in major hypertidal estuaries along Ungava Bay (Canada), highly predictable tidal-stream power could be an optimal and clean alternative resource for the off-grid Northern communities. However, it is important to understand how the cold and long Arctic winter affects the availability of this resource. The Koksoak hypertidal estuary was studied through instrumentation over one winter season and numerical modeling to address the knowledge gap. The coupled Delft3D-FLOW-Ice model was modified and used to model the ice-covered estuary and successfully calibrated and validated against in situ observations. Numerical simulations showed that although the tidal-prism discharge diminishes under the presence of ice, the tidal-stream power potentials still remain very high. Besides, the in situ observations demonstrated an apparent tide-dependent modulation of ΔTΔT (the difference between water temperature and freezing temperature) with increased ΔTΔT during flood tides. This is a major benefit for tidal-stream deployment as any accumulation of frazil ice on the blades would be very short lived.