Travel has been hit hard, with tens of thousands of flights cancelled or delayed and people warned to avoid using their cars on treacherous roads if at all possible.

Some areas, including Indianapolis in Indiana, even made driving illegal except in absolute emergencies.

The icy blast has been caused by a 'kink' in the strong winds surrounding the North Pole, known as the polar vortex.

Conditions are expected to ease over the next couple of days, bringing temperatures at least back to freezing point or thereabouts.