The Christmas travel rush is on, and it's about a 2-percent increase from last year, making this year's holiday travel period the busiest on record. The auto club AAA says they expect more than 122 million Americans to hit the roads, rails, and skies through New Year's Day.  But severe winter weather in some parts of the country could make the journey treacherous.  

Airports and roads are packed as millions of people travel to visit family and friends, and as travelers are on the move, so are winter storms.

In the Pacific Northwest, heavy rains resulted in major flooding.  In Redding, California, one person died when an "atmospheric river" triggered dangerous flash flooding – and more could be on the way.

Meteorologist Dani Beckstrom warned, "We're talking life-threatening flash flooding on Wednesday, that's Christmas Eve, focused on the morning. That doesn't just create travel trouble; it can really lead to the threat for both life and property."

Major cities from Detroit to New York and Boston are bracing for a wintry mix of rain and snow that could snarl the morning commute and holiday travel.

"If you're dreaming of a White Christmas, your dreams will come true across New York State and New England. We have snow on the ground, and we have more on the way as we head into Tuesday," AccuWeather's Bernie Rayno said. 

The T.S.A. anticipates screening more than 43 million passengers between December 19th and January 4th. It's so busy, the FAA is planning on using limited military airspace if needed.

"Well, I have a stop in between. There's already a delay, so that's no fun," said holiday traveler Alencia Williams. 

In Southern California, the holiday travel crush is causing serious backups on the freeways and at airports.

"We're flying to Chicago, and our flight just got delayed by an hour and a half while we were in the Uber," said Liza Bahles of Chicago.

The auto club AAA says nearly 110 million people will travel by car, and some good news, according to Gas Buddy, the national average for a gallon of gas has fallen for the fourth straight week to $2.79 a gallon.