Overflowing rivers were receding in Missouri and Illinois on Friday after flooding swamped communities and forced towns to evacuate, with forecasters warning that rain-swollen waterways flowing downstream could menace Southern states.

At least 28 people have died in the U.S. Midwest since the weekend in rare winter floods, mostly when driving into flooded areas after storms dropped up to 12 inches (30 cm) of rain, officials said. Flooding in the Midwest usually comes in the spring as snowmelt swells rivers.

Dozens died in American storms that were part of a wild worldwide weather system over the Christmas holiday period which has also brought heavy floods and storms to Britain.

More than 100,000 people have had to evacuate from their homes in areas bordering Paraguay, Uruguay, Brazil and Argentina due to severe flooding in the wake of heavy summer rains brought on by El NiƱo, authorities said last week.

Weather is dominating conversation on social media over the holiday season after the international climate deal in Paris.

Close to St. Louis, Missouri on Friday, the water level on the Mississippi River, the second-longest river in the U.S., was falling on Friday after reaching near-record heights, the National Weather Service said.

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

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.

Towns farther down the Mississippi hoped their levees would resist rising river levels. Southern states like Louisiana and Mississippi will be affected in coming days, the National Weather Service said.

The Mississippi is expected to crest in the small town of Thebes, in southern Illinois, at 47.5 feet (14 meters) on Sunday, more than 1-1/2 feet above the 1995 record, the NWS said.

Workers in Tennessee were preparing for the Mississippi River in Memphis to reach flood stage over the weekend.

"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 River.

Major flooding was also occurring on the Arkansas River and its tributaries in that state, the NWS said.

Louisiana Governor Bobby Jindal declared a state of emergency to prepare for flooding.

"All that water's coming south and we have to be ready for it," 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."