"I've been downtown for 37 years and I have never seen anything like this," said Steve Schomaker, a partner in a local insurance company.
Rising rivers wiped out a railroad bridge elsewhere in Iowa on Tuesday, closed part of a Wisconsin freeway and forced residents along the Mississippi River to prepare for what could be the worst flooding in 15 years.
In Cedar Falls, a city of about 35,000 some 130 miles northwest of Des Moines, Donita Krueger was among those helping fill sandbags in hopes of holding back the water.
"If this breaks, the whole downtown will be flooded," she said. "Everything goes on down here. It would be a big hit to the community."
White, yellow and orange sandbags lined downtown. Tarps and plastic were taped to windows and doors.
In nearby Waterloo, fast-moving water swept away a railroad bridge used to transport tractors from a John Deere factory to Cedar Rapids. It also led the city to shut its downtown and close five bridges.
Rising waters also threatened Palo to the south. City officials there urged residents to evacuate, predicting flood levels as much as 2 feet higher than 1993 levels, which left much of the state under water.
City officials said they would give residents 15 sandbags per house until they run out. They opened a shelter in nearby Cedar Rapids and asked residents who leave town to call City Hall to leave emergency contact information and to place a white sheet on their door so officials would know their house was empty.
Floodwaters were threatening water treatment plants in several towns, Lt. Gov. Patty Judge said. Mason City's plant was knocked out of service Sunday after the Winnebago River broke through a levee, while officials in Des Moines hoped that releasing water from the Saylorville Reservoir would protect the capital city and its water treatment plant from flooding.
More rain was in the forecast for Wednesday and Thursday, and the impact won't be known until after the National Weather Service runs flood projection models, said Roger Less of the U.S. Army Corps of Engineers.
In Wisconsin, fixing the broken and nearly empty Lake Delton, where churning water carved a new channel and drained into the Wisconsin River, was only one of the challenges facing engineers and contractors on Wednesday.
The rising water Rock River near Johnson Creek threatened a bridge and shut down westbound lanes of Interstate 94, which links Milwaukee and Madison.
State and local officials were monitoring various dams where high water from days of storms threatened to make them give way.
And the forecast included what no one wanted to hear — more rain.
But Bill Borghoff, a National Weather Service meteorologist, said the inch or two of rain expected to fall Thursday would likely lead to dry conditions Friday, and a dry spell could be coming after another weather system moves through over the weekend.
"As we head into next week, it looks pretty dry for the most part," he said.
Federal Emergency Management Agency teams planned to start visiting flooded areas on Thursday. Wisconsin Gov. Jim Doyle said he would seek a federal disaster declaration when their work is finished.
In Minnesota, Gov. Tim Pawlenty signed an executive order Tuesday declaring a state of emergency in two counties hit by flooding in the state's southeast corner.
In Elnora, Ind., about 100 miles southwest of Indianapolis, berms of white sandbags and concrete barriers held back the White River, leaving residents little choice but to wait and watch. Most residents left after voluntary evacuation orders came late Monday, two days after the area got up to 10 inches of rain.
Along the Mississippi River, the National Weather Service on Tuesday predicted crests of 10 feet above flood stage and higher over the next two weeks. Most of the towns are protected by levees, but outlying areas could be flooded.
"This is major flooding," weather service hydrologist Karl Sieczynski said of the Mississippi. He urged people in unprotected flood plain areas to seek higher ground.
Elsewhere, thunderstorms brought relief to parts of the East Coast that have been baking in a heat wave for four days. Temperatures in the upper 90s on Tuesday stretched from Georgia all the way to northern New England, where the weather service reported an afternoon high of 99 at Portsmouth, N.H.
The storms also knocked out power to hundreds of thousands of homes and businesses. About 160,000 customers in New Jersey, 110,000 in southeastern Pennsylvania, 35,000 in upstate New York and 20,000 in Connecticut remained without electricity early Wednesday.
Philadelphia officials blamed the deaths of two women on the heat wave.