Millions of Americans flocked to airports, train stations and highways Wednesday as they headed home for Thanksgiving.

Traffic was snarled for miles on Washington's Capital Beltway on Wednesday morning after a tanker truck carrying 8,700 gallons of gasoline exploded on Interstate 95 just north of the city around 5 a.m.

Drivers who stopped near the scene in suburban Beltsville, Md., were told to get out and abandon their cars for fear or a larger explosion, but no injuries were reported. The tanker's driver was able to escape.

"This is not what we needed to start this travel day," said Lon Anderson, spokesman for AAA Mid-Atlantic.

"You wouldn't want to be there today," Mary Yacko, 79, of Elkins Park, Pa., said of I-95 as she waited for a train from Philadelphia with her daughters to Chantilly, Va. She planned to drive back through the Washington area Sunday. "I know that trip will be horrible."

Snow was already falling Wednesday morning across parts of Michigan, but Kate Kehoe said she wasn't too worried about her trip from Ann Arbor to Flint.

"I'm glad gas is not $3 anymore," the preschool teacher said Wednesday morning.

Snow showers fell as far south as North Carolina, where Mount Mitchell had collected 10 inches overnight; snow in Indiana contributed to numerous wrecks during the morning rush but no serious injuries were reported.

"It's the first snowfall of the year and people don't have the winter habits yet," said state Trooper Robert Brophy at Fort Wayne, Ind. "Every year at the first snow, people forget how to drive since the end of last year's snow."

The Air Transport Association, which represents major airlines, predicts 21.7 million people will fly on U.S. airlines over the Thanksgiving travel season between Nov. 19 and Nov. 29, slightly more than the record number that took to the air a year ago.

"Air fares are up probably roughly $40 ... since last February, but that hasn't deterred people," Terry Trippler, an airline analyst with CheapSeats.com, told AP Radio.

Workers at the Federal Aviation Administration 's central command in Herndon, Va., expect about 55,000 scheduled commercial flights will take to the skies Wednesday; that number does not include private or charter aircraft. That means 5,000 to 6,000 flights could be in the air at any given hour.

Low visibility in the Chicago area was causing 15-minute delays early Wednesday. The city's O'Hare and Midway airports expected to handle nearly 2 million passengers during the holiday weekend, said Chicago Department of Aviation spokeswoman Wendy Abrams.

Some travelers, heeding warnings about delays on Wednesday, left a day early.

"I wanted to beat the rush," Joe Lamport said Tuesday after arriving at Hartsfield-Jackson Atlanta International Airport. The 35-year-old New York City man brought his family to Atlanta to spend the holiday with his brother-in-law's family.

Lamport wasn't alone. The airport reported 289,597 passengers on Tuesday — nearly 4,100 more than what's expected for Wednesday.

Lines were longer than last Thanksgiving at Minneapolis-St. Paul Airport on Wednesday because the Transportation Security Administration had cut back on screeners, said Patrick Hogan, a spokesman for the Metropolitan Airports Commission, which operates the airport.

Some travelers at Miami International Airport said conditions were surprisingly normal. "So far so good," said Miami resident Rosemarie Wilder, 61, heading to Atlanta with her daughter and granddaughter.

But people who weren't accustomed to Miami International didn't share her opinion. "It's like a hurricane," Martha Bittencourt, 54, of Sao Paulo, Brazil, waiting for a flight to visit friends in Tennessee.

The check-in area at Detroit Metropolitan Airport's McNamara Terminal was practically vacant Wednesday morning.

"This is the fewest I've ever seen in the airport, let alone for a holiday weekend," Chris Spangler of Ypsilanti said after checking his bags for a flight to Richmond, Va.

Detroit airport spokesman Michael Conway said advance booking data showed that more people were flying to Detroit than from it for Thanksgiving.

AAA reported that more than 37 million people will be traveling over the holiday weekend, undeterred by more expensive gasoline, rental cars and hotel rooms.

Traffic was up at Dallas-based Greyhound Lines Inc., spokeswoman Anna Folmnsbee, although she said she didn't have passenger figures because most people buy their tickets on a walk-up basis.

And Amtrak spokeswoman Tracy Connell said 125,000 people last year traveled on Amtrak trains the day before Thanksgiving, up 80 percent from the 69,000 who ride the trains on an average day. Amtrak put an extra 60 trains in service this week in the Northeast Corridor, but many trains were already sold out, Amtrak spokesman Cliff Black told AP Radio.

Traffic was up at Dallas-based Greyhound Lines Inc., spokeswoman Anna Folmnsbee, although she said she didn't have passenger figures because most people buy their tickets on a walk-up basis.

Early Winter Warnings

Bad weather may hamper some travelers' trips, particularly if winter comes early this year.

According to AccuWeather.com and experts at Weather.com, an Alberta Clipper — which is basically a fast-moving storm — will move across the Great Lakes beginning Wednesday, bringing heavy lake-effect snow to Wisconsin, Michigan and even into Ohio late in the day. A mix of rain and snow is expected from central Wisconsin, through Chicago and into Kentucky, according to Weather.com. Midwest temperatures will be mostly in the 30s and 40s on Tuesday but will drop to teens and 20s for Thanksgiving Day

Bands of heavy snow in the Great Lakes area could make for dangerous driving conditions, especially between Buffalo, N.Y., and Erie, Pa. AccuWeather.som senior meteorologist Dale Mohler forecasts a foot of snow, with four feet possible, in some areas. Heavy snow should also fall north of Syracuse with blizzard conditions possible. New York and Boston will be in the upper 30s on Wednesday and mid 40s on Thursday.

Coastal regions in the Northeast will see rain and even some snow mixing-in by Thanksgiving morning

Shoppers in the Northeast who plan on lining up early Friday morning for some bargain shopping on "Black Friday" — the opening day of the holiday shopping season — will need to bundle up against a chilly northwest wind. Some temperatures could reach below freezing.

In the southern states, cool temperatures are expected Wednesday but it will be 15 degrees warmer than average over the southern plains and Texas with Dallas; it will be colder on Friday. The South will remain dry through Thanksgiving, with only a few rain and snow showers along the southern Appalachians.

Fog will again be the main concern across the Pacific Northwest Wednesday. Southern Arizona and the Southwest will not see any precipitation through Thanksgiving, according to Weather.com; high temperatures will mainly be in the 70s and even a few 80s.

FOX News' Catherine Herridge and The Associated Press contributed to this report.