The remnants of Hurricane Isaac were grinding slowing northward early on Saturday with its centre now deep into Missouri and the heavy rain stretching for hundreds of miles east into Illinois amid reports of tornadoes and high winds, meteorologists said.
Drought-stricken areas of Missouri and Illinois were easily absorbing the rain Friday and the system was expected to soak the region deep into Sunday, said Jayson Gosselin, meteorologist with the National Weather Service's St. Louis-area office.
"We have gotten pretty widespread light to moderate rain that has piled up," Gosselin said. "The rain is certainly going to help our drought situation up here."
Most places in the area were reporting 1 to 3 inches (2.5 cm to 7.5 cm) of rain by late on Friday and were expected to see up to 5 inches of rain through Sunday, though some might see"upwards of 5, 6, 7 inches," Gosselin said.
A wide swath of central Illinois from west to east was expected to receive similar amounts of rain as the system slowly passes through the state, the weather service said.
The weather service received reports of two tornadoes in Illinois and one in Missouri on Friday that caused what looked like fairly minor damage, Gosselin said.
Two possible storm tracks will probably be surveyed on Saturday, he said.
The rain has been fairly consistent, and due to drought conditions and low river levels there have not been any reports of flash flooding or river flooding so far in the area, he said.
The slow-moving tropical depression dropped up to 8.5 inches (21 cm) of rain in Pine Bluff, Arkansas, where there were several flash flood watches and warnings on Friday. Many more Arkansas cities reported rain totaling 5 inches (13 cm) or more.
The system was expected to gradually turn more east from the Mississippi River valley into the Ohio River valley by Saturday night, bringing heavy rain into the central Appalachians by Monday and Tuesday.
At least four deaths were attributed to Isaac in the Gulf Coast. Residents were cleaning up on Friday, looking for electricity to be restored slowly and energy companies were getting ready to resume operating offshore rigs.
Isaac was the first hurricane to strike the United States this year and hit New Orleans almost exactly seven years after Hurricane Katrina devastated the city, causing an estimated 1,800 deaths.
Isaac caused widespread flooding and property damage in the US Gulf Coast region. More than 500,000 homes and businesses remained without electricity across Louisiana, Mississippi and Arkansas on Friday afternoon.
The system lingered over New Orleans for the better part of two days, providing a first and successful test of the city's new $14.5 billion flood-control system assembled after Katrina.
Areas outside those flood protections fared worse.
At least one levee was overtopped southwest of New Orleans, leaving some homes under 12 feet (3.6 metres) of water.
New Orleans was struck by 20 inches (50 cm) of rain, many other locations in Louisiana and Mississippi logged more than 10 inches (25 cm) of rain.