Holiday travelers in the Midwest and in parts East and South were keeping a wary eye Friday on a band of foul weather that stretched across the nation’s midsection and that was threatening to mess up opening weekend of one of the year’s busiest travel periods.

Forecasters were predicting a stew of foul weekend weather, from freezing rain then snow in the north to torrential rain in the Ohio Valley and Appalachia and possibly even tornadoes in parts of the South.

The worst of the storm wasn’t expected to hit Midwest population centers until today, and although few flights had been cancelled as of midday Friday, the weather was taking a toll on air travel: FlightStats.com reported more than 1,900 U.S. delays, with the most at Chicago’s O’Hare, Denver International, and the three big New York-area airports.

The foul weather could cause headaches for the estimated 94.5 million Americans planning to travel by road or air during this holiday season, which runs from today through New Year’s Day. Concerns were similar to just a month ago, when a winter storm hit just as people were traveling for Thanksgiving.

Tom Griffith, a financial planner from suburban Little Rock, Ark., moved up his departure time for a two-day road trip to Cincinnati so he could get ahead of bad weather.

“The TV said severe weather would impact southeast Arkansas up to Memphis in the afternoon. My plan is to be past Memphis before noon,” Griffith said Friday. “I guess my biggest concern would be the wind with the semis on the interstates.”

Initial worries are mostly in the South and Midwest. Yet while much of the East awoke Friday to unusually warm weather for this time of year, the region was next in the storm front’s crosshairs, creating pre-Christmas travel worries from Chicago and Detroit to Boston and New York.

Temperatures that hovered in the 60s in some parts of the Midwest on Thursday plummeted overnight, and freezing rain Friday morning snarled traffic and forced some school closures in Michigan and Wisconsin. The Wisconsin Department of Transportation said Interstate 90/94 was ice-covered from Tomah and Mauston. The state was bracing for significant snow, sleet and ice.

The National Weather Service issued a flash flood watch from Arkansas northeastward through parts of Missouri, Illinois, Indiana and Ohio, with up to 4 inches of rain projected. With falling temperatures, some of that could be freezing rain by tonight in the St. Louis area, weather service meteorologist Jon Carney said.

Forecasters said thunderstorms would likely develop in the South. The area that was most in peril stretched from central and northeastern Texas through Louisiana, Mississippi, Arkansas and southeast Missouri, where 80 mph wind gusts and flash flooding were possible.

By Sunday night, the storm systems will be hammering the East Coast. Some New England and mid-Atlantic states could see rare winter thunderstorms.

Tom Kines, an AccuWeather meteorologist, said the unsettled weather comes as a cold front in the northern U.S. clashes with unusually warm and humid air coming up from the South. He said that warm air will lead to record or near-record highs in many places over the next day or two. Nashville could reach into the 70s today. New York City could approach 70 degrees on Sunday.

The warm air will bring plenty of trouble to some areas.

“I think there’s a high likelihood there will be severe storms with hail and damaging wind” in parts of the South, Kines said. “Whether or not there’s tornadoes, that’s tough to say, but I will say the conditions are right.”