(CNN)Three-quarters of Americans are expected to stay home this holiday season, according to AAA.
But the other 85 million who might travel from December 23 through January 3 should keep an eye on the weather, as several systems will be moving across the country.
Atlanta Hartsfield-Jackson International Airport expects less than half as many holiday travelers as last year, officials said.
The Centers for Disease Control and Prevention (CDC) does not recommend traveling this holiday season, saying that it is safer to celebrate at home.
December 27 is projected to be the busiest travel day at the world's busiest airport. More than 2.1 million passengers will travel through it between December 17 and January 3.
The question is, will Mother Nature cooperate?
A white Christmas for some
A "white Christmas" brings at least an inch of snow on the ground in the morning, according to the National Oceanic and Atmospheric Administration (NOAA).
It's possible in the Northeast, where a storm dumped more than 3 feet on some parts. Temperatures before Christmas shouldn't top 40 degrees in most of those same areas, so some could stick around by then.
Plus, several storm systems are expected this week that might drop a few more inches.
In the western mountains, a decent depth is already on the ground, with more powder expected this weekend from Washington state through Wyoming.
Starting next week the models begin to vary widely about which areas are likely to get snow or rain.
For example, Chicago could get no snow under the American model -- or up to 8 inches in the European model.
Minneapolis is the opposite. The American model favors snow there, forecasting 8-12 inches, while the European model has none.
The American model also has snow as far south as Huntsville, Alabama, where 2-4 inches is forecast. The other model has nothing.
Both models agree on snow in a few cities, but the timing and accumulation varies. Pittsburgh, for example, is forecast to pick up 2 to 4 inches in the European model or 6 to 10 in the American.
St. Louis will feel like it's having two different seasons this week, going from a high in the mid 50s Monday down to a high only in the upper 20s by Thursday.
Denver is forecast to have a high of near 60 degrees Tuesday, then quickly drop to a high of only around 30 the next day.
The start of the week will be balmy for the central portion of the country, when temperatures will range from 15 to 25 degrees above average from North Dakota down through Texas. As that warmth spreads east on Wednesday and Thursday, it will be replaced by much colder air. By Thursday temperatures will average 10 to 15 degrees below normal from Minnesota to Mississippi.
By Christmas Day, Indianapolis, Cleveland, and Washington, DC, will have high temperatures about 15 degrees below normal.
Even South Florida will see cooler temperatures. Miami, Tampa, and Orlando will all have high temperatures averaging about 10 degrees below normal on Christmas Day.