Updated

The freeze that lingered over much of the nation Wednesday was expected to be followed by strong winds and more bitter cold through the Midwest and deep into the South.

The unusually persistent Southern cold snap has been blamed for at least six deaths and threatened to freeze Florida citrus crops.

The cold was expected to continue through the weekend. The National Weather Service predicted the heaviest snow from the fast-moving system would fall on Iowa, Missouri and Illinois, with 4-6 inches predicted along with some locally heavier amounts through Thursday.

In a rare turn for the South, forecasters warned that snow and ice were possible Thursday from South Carolina to Louisiana and wind chills in the region could get down to near zero at night.

"This air mass originated on the ice cap at the top of the world," said Bobby Boyd, a weather service forecaster in Nashville. He said the cold shot wouldn't be spent until it plunged southeastward and moved well beyond Cuba into the Caribbean.

Authorities said four people in Tennessee, one in Mississippi and one in South Carolina have died from the cold since the weekend. They included a man with Alzheimer's who wandered out into his yard in Nashville and froze to death, and a homeless man found dead in a tent in South Carolina.

The total doesn't include people who died in car accidents on icy roads and in fires started by stoves and space heaters.

The frigid weather hampered northern firefighters and even made life hard for Florida's tree dwelling iguanas.

In central and south Florida, farmers tried to salvage citrus and vegetable crops by spraying them in protective layers of ice and covering them in plastic.

It was so cold in Florida, freezing iguanas were seen falling out of trees. Experts say the cold-blooded reptiles become immobilized when the temperature falls into the 40s and they lose their grip on the tree.

In Indianapolis, frozen hydrants frustrated firefighters as they tried to put out a Tuesday night blaze at a commercial building.

Officials said the city of Des Moines is likely to exhaust the remainder of its $3 million annual snow removal budget with this week's storm, expected to dump up to as much as 10 inches of snow in some areas. That is on top of the more than 28 inches of snow that fell there in December.

Oklahoma's two largest school districts have canceled classes for the rest of the week because of subfreezing temperatures. Some of the schools in several other states, including Mississippi, Alabama and Missouri, were expected to close Thursday because of the weather.

In the Dakotas, Interstate 90 between Rapid City and Mitchell in South Dakota was closed Wednesday because of zero visibility that led to backed-up traffic and some crashes.

Joe Dietrich, who owns a snowblower repair shop in Bismarck, N.D., said bitter cold and snow have been so good for business, he had to turn away dozens of repairs this week.

"My building is only so big and I can only take so many," he said.

Kentucky Gov. Steve Beshear has declared a state of emergency in Perry County, where water line breaks have left large swaths of the area without water.

Much of the Blue Ridge Parkway in North Carolina and Virginia was closed to motorists because of heavy accumulations of snow and ice as well as downed trees.

In Maine, a pilot died Monday after he reported ice buildup on the wings of his small plane and it crashed into a river channel. Searchers were also looking for an 18-year-old snowmobiler who disappeared on New Year's Day. And in Wisconsin a 7-year-old boy died when he fell through ice into a river while sledding with friends.

In coastal North Carolina, volunteers were scrambling to save endangered sea turtles that were stunned by the cold and stranded off the Outer Banks.

Southern supermarkets were doing a brisk business in staples like bread and milk.

Ann Warden of Brentwood, Tenn., loaded eight grocery bags into the trunk of her black luxury car Wednesday morning and worried about a snowy forecast.

"You know Nashville gets paralyzed with just one snowflake," she said. "I couldn't be caught without milk. And I got some nice wine at the liquor store."