North American freeze: What is a polar vortex?
As the east cost of America prepares to face dangerously cold temperatures that have already hit the Midwestern states, meteorologist Jacqui Jeras explains what a polar vortex is to the BBC's Katty Kay.
As the east cost of America prepares to face dangerously cold temperatures that have already hit the Midwestern states, meteorologist Jacqui Jeras explains what a polar vortex is to the BBC's Katty Kay.