In the Plains and Midwest, seemingly every community was under some sort of watch or warning.
Alex Sosnowski, a meteorologist for AccuWeather, said the storm's biggest punch had come from its intense rainfall: "There's been a general 3 to 6 inch swath of rain from portions of Oklahoma all the way up to southern Wisconsin."
The system will thin out as it heads east but could still spell trouble in the Appalachian Mountain region Friday and in some spots along the East Coast by Friday night, Sosnowski said.
Midwesterners will be glad to see it go.
In Clarksville, Mo., a small, scenic Mississippi River town about 60 miles north of St. Louis, some 100 people were working feverishly to build a makeshift levee of gravel, plastic overlap and sandbags in a bid keep downtown dry. The heavy rain caused a sudden surge in the river, with a crest expected by early Sunday.
"I'm confident it will work, but I'm not confident we're going to get it done in time," Clarksville resident Richard Cottrell, 64, said of the sandbag levee. "It's a race against the clock."
City Clerk Jennifer Calvin said the Federal Emergency Management Agency was bringing in 500,000 additional sandbags, but the nearest available gravel had to be trucked in from nine miles away, and there weren't enough available trucks to expedite the effort.
The Mississippi is expected to crest 8 to 12 feet above flood stage at several spots in Iowa, Illinois and Missouri. The Missouri River was also expected to exceed flood stage by up to 10 feet at some Missouri locations.
Other rivers were rising quickly, too.
The town of Wyoming, Mich., evacuated about 25 homes in the path of the flooding Grand River. The Grand Rapids suburb called in all available police, firefighters and public works employees to help with sandbagging.
In suburban Chicago, Nick Ariano helped rescue a friend's grandmother, who became trapped in a home filling with water after a branch of the flooding DuPage River spilled over its levee.
Ariano, his friend and another man raced to a sporting goods store to buy inflatable rafts, then paddled out to the home and got Mille Andrzejewski, in her mid-80s, to safety. The three friends got some enjoyment out of the raft ride, despite the eeriness of floating over submerged cars and mailboxes.
"As kids growing up we used to raft down the river," Ariano said with a laugh.
About 60 miles southwest of Chicago, Morris Hospital in Grundy County began evacuating 44 patients to other hospitals after a nearby creek and the Illinois River rose and water crept into the basement, spokeswoman Janet Long said. Elective surgeries scheduled for Friday were canceled, although the emergency department remained open, the hospital said on its website.
In Gary, Ind., a flood-fighting drill scheduled for Friday was canceled — because of real flooding. Sandbagging operations were under way along the Little Calumet River.
Flash flooding was common. In Utica, Ill., the fire department evacuated a mobile home park. In Marshall County, Ill., boats were needed to rescue trapped morning commuters.
In Ava, Mo., a school bus carrying several children stopped because of water on the road. The driver turned around to go back, only to find flooding behind him, too. The driver and kids waited at a nearby home until help arrived.
Perhaps the storm's most bizarre scene came in Chicago, where a massive sinkhole opened and swallowed two parked cars and one that was driving through. The driver was hospitalized but was expected to survive.
Flooding from all-night rain storms forced authorities to close sections of several major expressways around Chicago, canceled classes at some schools and scrapped around 550 flights at O'Hare International Airport.
The storm-swollen Chicago River was being allowed to flow into Lake Michigan, in part to relieve sewer backups. Meanwhile, workers were furiously filling sandbags and putting up barricades along the Chicago River's north branch. The river was diverted away from the lake more than a century ago to keep pollution out of the lake, the source of the city's drinking water.
Winds, possibly from a tornado, damaged dozens of homes in Spavinaw, Okla., injuring one person. Another twister damaged a few buildings near Paris, Mo. High winds also blew two tractor-trailers off a highway near Monroe City, Mo.
In Kansas, large hail was blamed for an accident that injured six high school students and their teacher. The Kansas Highway Patrol said the wreck happened Wednesday on Interstate 70 near Russell. The group was returning to school from an art exhibition when the teacher lost control of the SUV and struck a car.
The U.S. Nuclear Regulatory Commission said a lightning strike knocked out power to a northern Illinois nuclear plant for several hours Wednesday night, but emergency generators kicked in to keep the site running. Exelon Generation said reactors will remain offline until safety checks and procedures are completed.
Up to a foot of new snow was expected in northern Minnesota. Duluth has already received 24 inches of snow this month, and the additional snowfall could push it past the April record of 31.6 inches set in 1950
Snow and ice forced closure of sections of Interstate 70 and Interstate 25 in Colorado. The Wyoming Department of Transportation warned drivers to watch for black ice.
The snow didn't bother 63-year-old Bill Zubke, a retired motivational speaker who was relaxing in the lobby of a downtown Sioux Falls, S.D. Zubke, from Watertown, S.D, described the unpredictable weather as "just April in South Dakota," though temperatures ordinarily reach into the 60 this time of year.
"We're South Dakotans," he said. "We can handle it."