Ice and freezing rain are expected into Wednesday morning, possibly mixed with sleet and snow.

The freezing temperatures gripping North America have already caused part of the Niagara Falls to ice over.

Horseshoe Falls, one of three waterfalls in the national park, has been turned into a wall of ice.

Normally, 681,750 gallons of water would thunder over the edge every second, but instead tourists have been greeted by a frozen wonderland.

Forecasters have warned of more freezing weather across the continent, which is suffering temperatures as low as -38 degrees in some states. The previous lowest temperature recorded in the US was -35 in 1924.

CNN meteorologist Taylor Ward said "The cold is here to stay and the worst is yet to come."

In New England, six to 12 inches of snow is expected, and a total of 50 states have recorded temperatures below freezing.

The ferry service in New York has been suspended.

The plunge in temperature has been so severe three sharks were washed up frozen on beaches in Massachusetts.

There have even been rare snow flurries in the normally temperate south, and in Texas several weather-related car crashes have been reported.