Weather Events 2019 - Polar Vortex warnings (1) (USA & Canada) - BBC News - 30th January 2019
The 'Polar Vortex' is a particularly cold air from the north sweeping down from the Arctic across North America at this time and can be dangerous from even speaking in. Also a a forecast explaining the movement of the vortex itself.
There is a second report here, with lots more images and dramatic footage in some cases (2):
Part of the "Weather Events (usually extreme) 2018+" series (on this channel), See play list "Weather Events (usually extreme) 2018+" for more. Includes reports, unusual & unseasonal occurrences.