(Reuters) - Residents of southern states along the Mississippi River are bracing for the flooding that has swamped communities from the Ohio River Valley to eastern Oklahoma over the last week, causing thousands of evacuations and killing at least 31 people.

Officials in Louisiana are checking levees daily, and Exxon Mobil Corp has decided to shut its 340,571 barrel-per-day refined products terminal in Memphis, Tennessee, as floodwaters threatened to inundate the facility just south of the city’s downtown.

“All that water’s coming south and we have to be ready for it,” Louisiana Lieutenant Governor-Elect Billy Nungesser told CNN. “It’s a serious concern. It’s early in the season. We usually don’t see this until much later.”

Workers in southwestern Tennessee were preparing sandbags on Friday in hopes of limiting damage from the Mississippi when it crests at Memphis next week, state emergency management officials said. Officials were also examining levees, to make sure they would hold.

“We’re moving things up high and we’ve got our generators out and got some extra water,” said Dotty Kirkendoll, a clerk at Riverside Park Marina on McKellar Lake, which feeds off the Mississippi.

Flooding in the U.S. Midwest typically occurs in the spring as snowmelt swells rivers. Freezing temperatures that have followed the rare winter flooding have added to regional woes.

Most of the deaths in Illinois, Missouri, Oklahoma and Arkansas have been caused by people driving into flooded areas after days of downpours. The dead included a central Illinois teenager whose body was recovered on Friday near where a truck in which he was riding was found the day before. Another teen from the truck was still missing.

Authorities also continued searching on Friday for country singer Craig Strickland, who had gone duck hunting on an Oklahoma lake during stormy conditions. His friend, Chase Morland, was found dead on Monday.

Twelve Illinois counties have been declared disaster areas, and Governor Bruce Rauner on Friday ordered Illinois National Guard troops into flooded areas in the southern part of the state to mitigate flood damage and help with evacuation efforts.

The Mississippi is expected to crest at Thebes, in southern Illinois, at 47.5 feet (14 meters) on Sunday, more than 1.5 feet above the 1995 record, the National Weather Service (NWS) said.

Flood warnings were also in effect on Friday for parts of Texas, Oklahoma, the Carolinas, Alabama and Kentucky, the NWS said, while major flooding was occurring on the Arkansas River and its tributaries in that state.

Dozens have died in U.S. storms, which also brought unusual winter tornadoes and were part of a wild worldwide weather system over the Christmas holiday period that also saw severe flooding in Britain.

More than 100,000 people were forced to evacuate their homes in areas bordering Paraguay, Uruguay, Brazil and Argentina after floods due to heavy summer rains caused by El Niño, authorities have said.

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Global weather dominated conversation on social media over the holiday season after the international climate deal in Paris.

Particularly hard hit in the United States in recent days has been Missouri, which has suffered historic flooding.

Close to St. Louis on Friday, the Mississippi, the second-longest river in the United States, was falling after reaching near-record heights, the NWS said.

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The Meramec River, which meanders near St. Louis and empties into the Mississippi, broke height records on Thursday, sending a deluge of water over its banks and forcing the closure of two major highways.

Interstates 55 and 44 reopened on Friday, but many other roads remained closed in the St. Louis area, state officials said, causing extreme traffic congestion.

Thousands of people evacuated from their homes earlier in the week were waiting to return to their communities and begin the process of cleaning up. Hundreds of structures have been damaged or destroyed, local officials said.