(CNN) -

Wicked wintry weather that pummeled the West Coast is now barreling across the country, threatening to wreck millions of holiday travel plans just before Thanksgiving.

Scores of car crashes and 12 fatalities are blamed on the storm.

Nearly 200 flights out of Dallas-Fort Worth International Airport were canceled Monday, in addition to the nearly 300 canceled Sunday.

Parts of Lubbock, known for its warmth and flatness, turned into a snowboarding park as several inches of snow covered the western Texas city.

Sleet and freezing rain will continue blanketing parts of the Southern Plains and Southern Rockies on Monday.

And after the storm deluges parts of the South with rain Monday evening, it'll start zeroing in on the Northeast, the National Weather Service said. And that could spell more travel nightmares.

How cold is cold?

An Arctic air mass will probably keep temperatures 15 to 20 degrees below normal along the East Coast through Thursday. But even if the system fails to deliver heavy snow, fierce winds could still hamper air travel, forecasters said.

Airlines flying in and out of Dallas/Fort Worth International Airport "pre-canceled about 300 departures to reduce the number of stranded travelers" Sunday in anticipation of the harsh weather, the airport's official Twitter account said. And 10% of flights at Oklahoma City's Will Rogers World Airport were also canceled because of the weather Sunday.

Then there's the snow. New Mexico could see up to 8 inches accumulating through Monday.

Massive rainfall, too

Heavy rain is expected to fall from Texas to Georgia on Monday and over the Carolinas on Monday night, with some sleet and snow mixed in for northern parts of that swath. The heaviest rain is expected across parts of Mississippi, Alabama, Georgia, Florida and South Carolina.

By Tuesday, the rain will reach the mid-Atlantic states and parts of the Northeast. And that could turn into freezing rain in the southern and central Appalachians.

Deadly road conditions

Five people have died in weather-related crashes in Texas, the Texas Highway Patrol said Monday. Sgt. Chris Ray said half of his deputies handled 71 accidents over the weekend, and that number will rise when the other deputies report accident totals. The central Texas Panhandle seemed to be hardest hit, he said.

Three of those killed in Texas were in a pileup on icy Interstate 40 in northwest Texas late Friday, Ray said. One of them was a man who got out of his car to help, and got struck. And at least 20 people were hospitalized from collisions within three miles of the fatal pileup, the Oldham County Sheriff's office said.

Four people have died in Oklahoma since Friday, Betsy Randolph of the state's Department of Public Safety said. In each case, the driver was going too fast for conditions, she said. Randolph said only one of those killed was wearing a seat belt.

Two people died in New Mexico in dangerous road conditions. A 4-year-old girl who was not properly restrained was killed Friday when the car she was riding in slid off icy U.S. Highway 70, the state's Department of Public Safety said. On Saturday, a woman in her 50s died when the pickup that she was riding in rear-ended a semi-truck in heavy traffic near Gallup, New Mexico, state police said.

In Arkansas, authorities investigated 18 crashes in a two-mile section of Interstate 540 Monday morning, according to Lance King, troop commander for state police. The largest was a three-car pileup. Three people were transported from the scene, and there were no fatalities, he said.

In Yuba County, California, a 52-year-old died when a tree fell on top of a vehicle Thursday, the county sheriff's office said.

When will this storm end?

By Thanksgiving Day, the storm will be giving the Northeast a layer of snow.

But much of the country will enjoy calm Thanksgiving weather -- even if it's a little more frigid than usual.