An Arctic blast is set to bring record cold and wintry conditions to much of the U.S., affecting two-thirds of the nation from Monday.

The cold air, breaking off from Canada’s polar vortex, puts over 84 million people under alerts for freezing temperatures, winter weather, and snow in cities from New York to Dallas and Florida.

Snowfall of 12–18 inches is possible in parts of the Midwest and Appalachians, with intense lake-effect snow causing dangerous travel conditions in areas including Michigan, Indiana, and Wisconsin.

Southern cities, including Miami, Atlanta, Birmingham, and Memphis, could see record lows, with temperatures 10–25 degrees below normal, while freeze warnings threaten crops, infrastructure, and outdoor activities, NBC News has reported.

States including New York and Mississippi have activated emergency measures, deployed snowplows, and urged residents to prepare for extreme cold and hazardous conditions.