Americans across the Midwest and South will have to break out their umbrellas and plan for extensive delays during the always-busy Thanksgiving travel week, weather forecasters said Friday.

Tuesday looks to be the week's toughest day of travel with a storm system, stretching from Chicago down a straight line south to New Orleans, soaking holiday travelers.

There's a 90-percent chance of rain for the Windy City that day, a 70-percent likelihood of precipitation in Memphis and a 40-percent shot of raindrops on the Big Easy. The Chicago rainfall could total as much as 1.5 inches.

"So many of us will be traveling, Monday is a good travel day in and around Chicgao. Tuesday? Not so much," said Paul Deanno, a meteorologist for NBC Chicago.

There might be a point where rain turns to snow by the end of Tuesday and early Wednesday.

"Don't marry yourself to the forecast predictions of just rain," Deanno warned. "We could be looking at rain or snow on Tuesday."

Then by Thanksgiving Eve, much of the nation, coast-to-coast, should experience at least some rainfall.

Up to 1 inch of rain might fall on normally sunny Southern California on Wednesday. A half-inch could fall on major U.S. cities such as Dallas, Atlanta and Boston on that day.

"We've got our second storm of the season arriving next Wednesday and Thursday which means Thanksgiving is going to be cooler and wetter this year," said Shanna Mendiola, a meteorologist for NBC Los Angeles. "So our holiday, looking wet and cold."

The Automobile Association of America (AAA) estimated that more than 55 million Americans will take to the roads and skies for Thanksgiving-related travel of 50 miles or more away from home.

It's set to be the second-highest Thanksgiving travel volume since AAA started making these estimates in 2000, trailing only the record set in 2005.