It's bitterly cold on the US East Coast, where temperatures have fallen dangerously low in some places.

A powerful blizzard has left people from northern Florida to New England facing temperatures as low as -40 Celsius.

New York Mayor Bill de Blasio said while workers are out trying to clear snow and ice, the situation isn't good.

''It has intensified in the last few hours.''

''I am now declaring a winter weather emergency for New York city.''

Hundreds of schools are closed and major airports have shut down because of whiteout conditions.

Nearly 500 members of the National Guard are helping with the emergency response.