The American side of the Niagara Falls are an icy blue after a prolonged period of extreme cold in Niagara Falls, Feb, 20 2015.

Much of the United States and Canada are experiencing unusually cold weather with record low temperatures and the wind chill factors making it feel well below freezing.

A partially frozen American Falls, due to subfreezing temperatures, is seen when the temperature dropped to 6 degrees Fahrenheit (-14 Celsius) in Niagara Falls, Ontario Feb. 17, 2015,

There was one instance in March 1848 when the river stopped flowing, but this was actually due to a large ice jam upstream.

The American side of Niagara Falls becomes an increasingly beautiful ice sculpture after a prolonged period of extreme cold in Niagara Falls, Canada, Feb. 20, 2015.

A frozen cliff face on the American side of the Niagara Falls in Niagara Falls,Ontario Canada, Feb. 20, 2015.

Steam rises from the nearly frozen American side of the Niagara Falls after a prolonged period of extreme cold in Niagara Falls, Ontario Canada, Feb. 20, 2015.

Niagara River keeps flowing below the ice cover, so the mist continues to rise, freezing on the surrounding surfaces.

Sightseers have flocked to the area to see the nearly frozen Niagara Falls in Niagara Falls, Ontario, Canada, Feb. 20, 2015.

The impressive ice buildup near the brink, as well as mountains of ice nearly 50 feet thick, has become a tourist magnet for the second straight year.

A sightseer takes a picture of a nearly frozen Niagara Falls on  in Niagara Falls, Ontario, Canada, Feb. 20, 2015.

The American Falls is one of three waterfalls that make up the natural attraction.

Steam rises from a nearly frozen Niagara Falls in Niagara Falls, Ontario, Feb. 20, 2015.

Extreme athlete Will Gadd ice climbs the first ever ascent of Niagara Falls in Niagara Falls, New York, Jan. 27, 2015.

The idea of ice climbing Niagara Falls took root in 2014 when the "polar vortex" froze large parts of the Falls. Working in collaboration with Red Bull the permit for the climb came through three days before the ascent after Gadd submitted a very exhaustive safety plan.

Will Gadd ice climbs the first ascent of Niagara Falls in Niagara Falls, New York, Jan. 27, 2015.

Working in collaboration with Red Bull the permit for the climb came through three days before the ascent after Gadd submitted a very exhaustive safety plan.

Niagara Falls freezes over due to subfreezing temperatures this week in Niagara Falls, Ontario Feb. 17, 2015. Temperatures dropped to 6 degrees Fahrenheit (-14 Celsius) with a windchill factor making it several degrees below zero.

A snow-covered landscape is seen over the frozen Niagara Falls in Niagara Falls, New York Feb. 17, 2015.

The American Falls is one of three waterfalls that make up the natural attraction.

A partially frozen American Falls is seen in Niagara Falls, Ontario Feb. 17, 2015.

A rainbow appears over the partially frozen American Falls (R) in subfreezing temperatures in Niagara Falls, Ontario Feb. 17, 2015.

A partially frozen American Falls in front of the skyline is seen in Niagara Falls, Ontario Feb. 17, 2015.

The National Weather Service said extremely cold arctic air would expand the ice covered area in the days ahead.

Visitors view frozen Niagara Falls in Niagara Falls, New York, Feb. 17, 2015.

A partially frozen Niagara Falls is seen on the American side during subfreezing temperatures in Niagara Falls, Ontario, March 3, 2014.

An old hydro building is seen behind Niagara Falls during subfreezing temperatures in Niagara Falls, Ontario, March 3, 2014.

A blue-hued partially frozen Niagara Falls is seen on the American side during subfreezing temperatures in Niagara Falls, Ontario, March 3, 2014.

A partially frozen Niagara Falls is seen on the American side during subfreezing temperatures in Niagara Falls, Ontario, March 3, 2014.

A partially frozen Niagara Falls is seen on the American side during subfreezing temperatures in Niagara Falls, Ontario, March 3, 2014.

A partially frozen Niagara Falls is seen on the American side during subfreezing temperatures in Niagara Falls, Ontario, March 3, 2014.

Lights create a multi-colored hue for the frozen Niagara Falls on the American side during subfreezing temperatures in Niagara Falls, Ontario March 3, 2014.

The frigid air and "polar vortex" that affected about 240 million people in the United States and southern Canada created a frozen American Falls in Ontario, Jan. 8, 2014.

A partially frozen cascading Niagara Falls seen from the U.S. side in Ontario, Jan. 8, 2014.