Larry Copeland, Doug Stanglin and Doyle Rice, USA TODAY
ATLANTA -- A "historic" winter storm engulfed the Deep South on Tuesday, bringing rare snow and the danger of icy roads to areas not accustomed to battling it and causing massive traffic problems across the region.
Snow flurries and sleet fell in Houston and its northern suburbs, and ice on overpasses made driving treacherous. Motorists from Texas to Virginia were warned to stay off the roads, while Louisiana and South Carolina declared states of emergency.
Popular warm-weather tourist destinations, including New Orleans and some Florida beaches, expected ice and snow over the next two days.
The weather caused more than 3,400 commercial flights to be cancelled, and another 2,000 saw major delays, according to Flightstats.com.
"This is a historic storm, for its size," according to meteorologist Mike Smith of AccuWeather Enterprise Solutions.
In Atlanta, one to three inches of snowfall caused massive traffic problems. Thousands of school children dismissed early, commuters who worked half a day and motorists driving too fast for conditions all combined to turn freeways and major roads into parking lots. At least 900 flights through Atlanta were among those cancelled.
Officials said hundreds of students may have to spend the night in classrooms or gyms. "They have food and we have gas heat and the electricity is on," DeKalb County Emergency Management Director Anthony Clifton said. "
In Alabama, the state House of Representatives adjourned for the day because of the weather. "There's not enough of us here today," said Rep. Dimitri Polizos, R-Montgomery. "It's crazy weather, and we can't control it."
Greenville, S.C., was expecting as much as two inches of snow.
"Greenville's beautiful but with a little bit of snow it's pretty amazing. It adds a little bit of charm," said downtown resident Willy Senza.
Ed Brewer, pastor of Bountyland Baptist Church in Seneca, S.C., said about a half-inch had of very fine flakes had accumulated there.
"My old mountain granny used to call this kind of snow "'chigger dandruff,'" he said, referring to a common name for mites that are a pesky irritant in the South.
A hard freeze was forecast across the South, along with heavy snow to some areas, particularly along the Carolina Coast and in Virginia, where a foot of snow was expected. There was a threat of icy roads in Austin, Charleston, S.C., Pensacola, Fla., Mobile, Ala., and New Orleans.
"This is is a very dangerous situation because snow and ice are very rare for extreme southern Mississippi," said Robert Latham, executive director of the Mississippi Emergency Management Agency. "We need everyone to have an emergency plan together for this."
At the same time, intense cold continued its onslaught across the north-central and northeastern U.S., with wind chill warnings and advisories in place all the way from Montana to Maine.
The storm will slowly move off the Southeast coast on Wednesday morning, the weather service reports. Snow, sleet and freezing rain will wind down in eastern portions of the Carolinas, southern Georgia and the panhandle of Florida by midday.
After a chilly start, temperatures are forecast to rise above freezing throughout the Southeast by early afternoon. The milder temperatures and mostly sunny skies should allow some of the snow and ice from Tuesday to melt. Even warmer weather is on the way for Thursday in the South.
AccuWeather predicts that the Great Lakes and Northeast will endure one more day of bitterly cold temperatures in the teens and 20s Wednesday before milder temperatures in the 30s and 40s return for Thursday and Friday.
However, after a brief warm-up Wednesday, the northern Plains and Upper Midwest will return to frigid single-digit high temperatures by Thursday.
The slippery roads caused hundreds of wrecks, many with injuries, across the region as drivers spun out and crashed into other drivers or slid off roadways.
In Savannah, schools were closed and residents were "making a run" on grocery stores, said Bret Bell, a city spokesman. He said the main concern was not so much snow as icing on roads during commuting hours.
"We received mocking, like other communities in the South, for canceling schools when we don't have any snow on the ground, but the last thing they want is school buses on ice-slicked roads," Bell said.
In declaring a state of emergency in Louisiana, Gov. Bobby Jindal warned that heavy snow and freezing temperatures could paralyze most roadways.
"We are working to keep open major corridors across the state, but only for those who absolutely must travel," he said.
In New Orleans and surrounding suburbs, sleet and icy streets forced road and school closures and grounded dozens of flights.
All federal government buildings and public schools in New Orleans were closed Tuesday, as were City Park and New Orleans Municipal Court.
The inclement weather also postponed the much-anticipated federal corruption trial of former Mayor Ray Nagin, which began Monday with jury selection.
South Carolina Gov. Nikki Haley declared a state of emergency at noon and activated the state's Emergency Operations Center.
The state's National Guard was standing by to assist first responders and state agencies.
Appalachian Power asked its customers in Tennessee, Virginia and West Virginia to conserve electricity and minimize the threat of power disruptions during the cold snap.
The utility says PJM Interconnection, which operates the electricity grid for 13 states and the District of Columbia, has issued a call for voluntary conservation because of expected high demand.
The harsh cold pushing into the South is an extension of the hard freeze that has gripped the Midwest for days. Schools in Chicago are closed for a second day.
In Minnesota, most metro schools and the University of Minnesota are closed as wind chills were expected to drop as low as 35 to 50 degrees below zero.
The state was also struggling with a short supply of natural gas in some parts due to a Canadian pipeline explosion.
Xcel Energy asked all customers, including in the Twin Cities, to cut back on natural gas use and hold their home thermostats at 60 degrees.
The pipeline blast near Winnipeg disrupted supplies of natural gas service for more than 100,000 Xcel customers in northwestern Minnesota, eastern North Dakota and western Wisconsin, the Star-Tribune reports.
Contributing: Rick Jervis, William M. Welch, USA Today; Brian Eason, Courier-Journal, in Jackson, MIss.; Ron Barnett, Greenville News; Brian Lyman, The Montgomery Advertiser; KHOU-TV; Associated Press