Residents in the flood-ravaged US state of Missouri waited anxiously Thursday to see how high the mighty Mississippi River would rise, as the death toll from the record-breaking deluge rose to 14.

Hundreds of homes and businesses have been swallowed by the frigid, muddy waters. Scores of people have had to be rescued by boat -- including one man plucked from the roof of his home as it floated away.

Governor Jay Nixon pleaded with people to heed evacuation orders and stay off flooded roadways, after the body of a motorist who was swept off a road was recovered on Wednesday.

All but one of the state's 14 fatalities were caused by people driving into the floodwaters and Nixon has stationed troops at major road closures to help direct traffic and stop people from driving around barricades.

"This historic flooding event will continue to cause significant hazards and disruptions -- from Missourians being forced from their homes, to businesses temporarily closing, to traffic congestion and impacts on interstate commerce due to the closure of a major trucking corridor," Nixon said in a statement.

"I thank the many Missourians who are assisting their neighbors by providing rooms in their homes, helping with sandbagging efforts and countless other acts of kindness."

- House hits a bridge -

The Mississippi River was forecast to crest in the city of St. Louis late Thursday at more than 12 feet (3.8 meters) above flood stage. Towns further downriver are forecast to see a crest that will be nearly 20 feet above flood stage in the coming days, according to the National Weather Service.

The recovery will be long and costly, local officials feared.

The mayor of hard-hit Fenton, Missouri watched in horror as a house swept away by the floods struck a newly-built bridge.

"It was kind of our pride of a new bridge being built. And you see that house hit it, was very nerve wracking," Michael Polizzi told CNN.

"We're really concerned about that."

The flooding has been so widespread he doesn't even know whose home it was that struck the bridge. Thankfully, nobody has been reported missing so far from his suburban St. Louis town.

President Barack Obama called Nixon from Hawaii, where he is on vacation, to offer federal assistance if it is needed.

"The president thanked the governor for his leadership during this challenging time and expressed condolences on behalf of the First Lady and himself for those who lost their lives," spokesman Eric Schultz said Wednesday.

The United States has been hit by a wave of wild weather -- tornadoes, floods and rain -- that has claimed at least 52 lives in the past week and stranded millions trying to get home after the Christmas holiday.

Nixon declared a state of emergency on Sunday and called in the National Guard Tuesday to help local officials deal with the rare winter flooding -- the result of a monster storm system that also unleased tornadoes and freezing rain.

Neighboring Illinois has also been hard-hit. The storm claimed the lives of five people swept away while driving on a flooded roadway, and a state of emergency was declared in a dozen counties.

The wild winter weather has killed 11 people in Texas, 11 people in Mississippi and six in Tennessee.

Alabama and Arkansas each reported two storm-related deaths while Georgia had one death.

More misery came Wednesday as heavy rain led to renewed flash flood warnings in Alabama, Florida, Georgia, North and South Carolina and West Virginia.

Significant flooding is currently occurring in more than a dozen US states, the weather service said.