The extreme cold battering parts of North America has led to a partial freezing of Niagara Falls. With temperatures below freezing, the falls are having a repeat from about eight weeks ago, when the "polar vortex" created a similar effect.
Here are some striking images from Mark Blinch at Reuters taken from the American side.
Reuters/Mark Blinch
Reuters/Mark Blinch
Reuters/Mark Blinch
Reuters/Mark Blinch