Mill Creek Falls - Super cool - literally.

I photographed the falls at Mill Creek near Kelowna on January 28, 2026.

 We know that water freezes at 0° C.  But it is possible for water to exist in a liquid state when the temperature falls below the freezing point.  Liquid water below 0° C is supercooled and has some very interesting properties.

Supercooled water occurs because of the lack of nucleation sites in the liquid.  Generally, this requires pretty clean water with little suspended solids.  You may see this when freezing purified water in your freezer at home - there is a video here showing the effect.  When disturbed, or if nucleation sites become available, the water will instantly freeze.

Another form of supercooled water is called frazil ice.  Fast-moving water can become supercooled and form tiny needle-shaped crystals.  Frazil ice can attach to cold rock or an icy surface and become part of the frozen mass.  Waterfalls can build up a substantial layer of ice when supercooled water, either from the lack of nucleation sites or the presence of frazil ice, flow over a rock surface such as what is found in a stream with waterfalls. 

It has been very cold recently here in the Okanagan, down to -14° C just a few days ago.  That is cold enough to cause water to become supercooled.  That water may then travel over a rock surface and instantly attach to it, providing a substrate for more supercooled water to solidify.  

I am sure that water also freezes in the traditional way, where we think that water above 0° C coats the surface of a structure below the freezing temperature and causes solidification.  But you can be sure that it is not the only mechanism involved in forming waterfall ice.

Thanks for reading.

Eric Svendsen     www.ericspix.com