Wintry conditions sweep across the U.S., producing below-average temperatures, winter weather watches and flood watches.

After a weekend of snow in the Midwest, the winter weather is focused farther south on Monday, with snow hitting Virginia, West Virginia and North Carolina.

Three states are facing possible "blizzard conditions" as a winter storm watch goes into place on Tuesday, the National Weather Service (NWS) warns.

More than 18 million people are under winter weather alerts across the West and Midwest as storms are forecast to bring heavy snows and bitter winds. A strong system is producing heavy snow across the Northern Rockies,

The National Weather Service issued an updated winter weather advisory at 2:24 p.m. EST on Monday valid from 11 p.m. EST until Tuesday 4 p.m. EST for Leelanau, Benzie and Manistee counties.

With snow falling, the National Weather Service expanded a winter storm warning to include Ames and surrounding Boone, Story and Marshall counties.

That’s because temperatures are going to plunge overnight, causing puddles and wet spots left on the roads to freeze. Forecasters expect lows in the low 20s in the Triangle and the upper teens not far north and west, turning wet surfaces to ice.

Winter storm warnings and advisories have been issued across nine states in the U.S. Stay with Newsweek for the latest updates.