Niagara Falls, which spans the border between the U.S. state of New York and the Canadian province of Ontario, is a natural wonder composed of three distinct sections: the Horseshoe Falls, the American Falls, and the smaller Bridal Veil Falls. While the falls never stop flowing completely, the answer to whether this spectacle actually freezes is more complex than a simple yes or no. The stunning winter scenery often creates a deceptive, crystallized illusion of being frozen solid.
The Annual Phenomenon of Ice Formations
During periods of extreme cold, the falls take on a spectacular, frozen appearance as the mist and spray generated by the plunging water freeze into a thick, opaque shell. This accumulated ice forms towering “ice falls” and miniature glaciers along the rock face, giving the impression that the entire cascade has stopped. However, even when temperatures drop well below freezing, the immense volume of water continues to rush underneath this frozen crust.
The American Falls, which carries only about 7 to 10 percent of the Niagara River’s flow, often appears much more frozen than its larger counterpart. Its reduced water volume allows spray and ice buildup to more easily cover the falling water, reducing the flow to a mere trickle over the surface. In contrast, the much wider Horseshoe Falls, which carries the majority of the river, never freezes solid and maintains a continuous, heavy flow throughout the winter season.
A historical winter feature was the “ice bridge,” which formed at the base of the falls when ice chunks were forced up from the river below and froze together, sometimes reaching a thickness of 40 feet or more. Before 1912, people would often walk across this natural crossing linking the American and Canadian sides of the gorge. Today, the formation of such a substantial, stable ice bridge is much rarer due to modern river management techniques.
The Role of Water Volume and Diversion
The primary reason the falls cannot freeze solid is the sheer volume and speed of the water flowing from Lake Erie into the Niagara River. An average of approximately 85 million liters of water pour over the falls every minute during the winter months. The constant turbulence of this flow prevents the entire body of water from reaching the temperature necessary to freeze completely, as the immense force of the water is too great to be overcome by the cold air alone.
Furthermore, a significant portion of the Niagara River’s flow is intentionally diverted upstream for hydroelectric power generation, a practice regulated by the 1950 Niagara Treaty. During the non-tourist season (typically November 1 to April 1), up to 75 percent of the river’s water is rerouted through tunnels and canals to power plants. This controlled diversion generates electricity and acts as a form of ice management, reducing the amount of water flowing toward the falls.
Since 1964, a steel pontoon structure called the “ice boom” has been installed near the mouth of the Niagara River at Lake Erie. This boom prevents massive sheets of ice from Lake Erie from entering the river and causing ice jams that could damage bridges and power intakes. The combination of diverting water and physically managing the ice upstream makes a natural, complete stoppage of the falls practically impossible.
Historical Instances of Flow Stoppage
Despite the river’s constant movement, the flow over the falls has been severely reduced or stopped only twice in recorded history. The only natural cessation occurred for about 30 to 40 hours in March 1848. This event was not caused by the falls freezing, but by an ice dam that formed upstream near Buffalo when strong winds drove massive ice floes from Lake Erie into the mouth of the Niagara River, effectively blocking the water source.
The second instance occurred in 1969, when the U.S. Army Corps of Engineers intentionally stopped the flow. For a period of five months, the American Falls was completely dewatered to allow geologists to study the rock face and remove unstable talus at its base. Engineers accomplished this by constructing a cofferdam to divert the American Falls’ flow entirely to the Horseshoe Falls.