Millions of residents across multiple states in the U.S. have been warned to brace for a possible bomb cyclone, forecast to hit from Monday, December 29, through to the weekend, bringing heavy winds and wintry conditions, prompting the National Weather Service (NWS) to issue storm warnings and advise drivers not to travel unless it’s an emergency.

Governor Tim Walz declared a peacetime emergency on Sunday, deploying the National Guard to help with emergency storm operations. The governor said the severe weather creates serious danger for travelers during one of the busiest times of the year. He thanked the National Guard for helping get stranded drivers to safety.

A winter storm watch alerts the public to the possibility of heavy snow, freezing rain or sleet. Winter Storm watches are usually issued 12 to 48 hours ahead of predicted severe weather.

A "bomb cyclone" is intensifying severe winter weather for millions of people across the U.S. The system is expected to knock out power and disrupt holiday travel.

Millions of Americans live in areas under winter storm alerts stretching from northern Minnesota to the Eastern Seaboard.