(CNN) - Millions of Americans traveling home from the holidays and a treacherous winter storm barreling through parts of the plains and the Midwest could be a recipe for disaster.
The weather threatens to thwart travel plans for Americans on one of the busiest days of the holiday season, and could continue to affect travelers in other parts of the country for days to come.
"Airports are already going to be absolutely insane because of people traveling home,” said CNN meteorologist Jennifer Gray. “Add to that the snow, the rain the severe weather threat and we could have pure chaos as far as travel goes."
More than 10 million people are under winter weather alerts across the region. The storm threatens up to two feet of snow in some areas, with eastern Colorado, western Nebraska and the Dakotas expected to be hit the hardest.
Heavy rain already began impacting some states on Wednesday morning, and meteorologists say it could all freeze as cold air comes through.
"The temperatures are really going to plunge on Friday, so whatever is on the road, rain or snow, it's going to freeze,” said meteorologist Christopher O’Brien.
And as fliers return from Christmas vacations or leave for New Year’s Eve destinations, they should expect long delays and potential cancellations.
“We’re looking at airport delays from Houston, Dallas, Kansas City, Minneapolis, Chicago, even New York and Boston,” said Gray. “And we know that can have a trickle effect across the country.”
Officials at the world's busiest airport - Atlanta’s Hartsfield Jackson - expected nearly 85,000 travelers on Wednesday.
For those planning to drive instead of flying, expect hazardous roads through Friday, with possible flooding in some areas from the Midwest even down through the Southeast.