CHICAGO » A mix of Gulf Coast thunderstorms expected to travel north, predicted snowfall in the Great Lakes and blustery conditions in the nation’s midsection threatened Tuesday to tangle holiday travel plans nationwide.

While snow fell in some Midwestern states — nearly 2 feet in South Dakota’s Black Hills — a strong storm system expected to drop rain along the East Coast and snow from Missouri to Michigan developed in Mississippi, Georgia and Louisiana, among other southern states. The severe storms in the South killed at least four people, damaged homes, businesses and cars, and knocked out power to thousands.

The storms led to some delays at Hartsfield-Jackson Atlanta International Airport — though airport spokesman Reese McCranie said in an email he was not aware of any cancellations. He said the airport did not expect a ground stop.

Meteorologists predicted rain-into-snow for parts of the Great Lakes region, with several inches of Christmas Eve snow expected in portions of Illinois. Officials at both airport hubs in the nation’s third-largest city readied for the potential of holiday delays and cancellations, particularly with more people expected to fly this year.

"I’d be nervous about the possibility of not being able to get out," said Chicago area meteorologist Charles Mott. "I would definitely make plans about possibly staying put or doing something else."

About 4.2 million passengers are expected through O’Hare and Midway international airports during an 18-day holiday travel period ending Jan. 6, said Chicago Aviation Department spokeswoman Karen Pride. That would be a 3 percent increase at O’Hare and a 9 percent jump at Midway compared to last year. Pride urged travelers to allow plenty of time and monitor airlines closely.

Elsewhere, a blast of cold and snowy conditions affected travel Tuesday.

Dozens of flights in and out of Philadelphia International Airport were canceled and others saw delays of about two hours due to bad weather and low clouds.

Just west of Green Bay, Wisconsin, a school bus was involved in three-vehicle crash on snow-covered, slick roads. No serious injuries were reported.

In eastern Colorado, Interstate 70 was shut down into Kansas for eight hours because of strong winds and blowing snow. Farther west, blowing snow also led to part of U.S. Highway 285 being closed at some points Tuesday.

Parts of western South Dakota saw snow accumulations of a foot or more through Tuesday morning. Higher elevations in the Black Hills got close to 2 feet.

But not all winter enthusiasts were so lucky.

Snow isn’t expected in other parts of South Dakota until Friday. Sioux Falls resident Alana Amdahl said she’s disappointed about the lack of snow projected for Christmas.

"We live in South Dakota for a reason," said Amdahl, 27. "We don’t have palm trees to put Christmas lights on, we have evergreens. Of course, we need snow. It can melt after the new year."

Snow was expected even in parts of Hawaii. A blizzard warning was in effect through Wednesday evening for the summits of Mauna Kea and Mauna Loa on the Big Island of Hawaii, where the National Weather Service says up to 8 inches of snow could accumulate above 11,500 feet. Snow on the mountains is common, but a blizzard is unusual.

Associated Press writers Regina Garcia Cano in Sioux Falls, South Dakota; Colleen Slevin in Denver; Phillip Lucas in Atlanta; Alex Chihak in Phoenix; and Michael Sisak in Philadelphia contributed to this report.