Hi, it is quite strange but frost like -5 for few weeks and the waterfall is under ice. It goes from a side and moving towards middle of the waterfall, the same as on the rivers. Also during cold winter time, there is not so much water flowing as in other seasons, all water is holded in snow and ice, sometimes the river is freezing in the upper part and the falls getting smaller and smaller until they can freeze completely. It is long term process but finally, after few months of winter, everything is frozen ;).