US weather: Seven states declare emergencies amid warnings snow could be heaviest in a decade – live updates

Snow, ice, wind and plunging temperatures creating dangerous travel conditions from central and southern states all the way to the East Coast

As we said earlier, the freezing weather is being blamed on disturbances in the polar vortex.

Daniel Adamson has more on this, including how the phenomenon has already led to temperatures as low as -40C in northern Canada.