Footage of a bubble turning into an icy sphere as temperatures drop to -35C in Canada.In the video, filmed in Regina, Saskatchewan, on December 28, a bubble appears to freeze into a solid sphere.Writes the filmer: "Frigid air does not mean you have to stay in. Bundle up, get out and create something amazing!"Temperatures across Canada and northern US have plunged since Christmas.Weather reports say this is due to a lobe of the polar vortex dipping far south over North America.