A powerful spring storm system stretching from southern Texas to northern Michigan unleashed a wave of weather extremes on the Midwest on Thursday and threatened to bring its mix of hard rains, high winds and severe thunderstorms to the East by the weekend.

The massive system was wreaking havoc from the Rockies to the Rust Belt. Up to a foot of snow was expected in parts of Minnesota and the Dakotas. Snow and ice closed highways in Colorado and Wyoming. Rivers surged beyond their banks from downpours in Missouri, Iowa and Illinois. Tornadoes caused scattered damage in Oklahoma. Hail caused a wreck that injured a high school teacher and her students. Lightning temporarily knocked out a nuclear power plant. Rain caused a sinkhole that devoured three cars in Chicago.

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 today 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, about 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.

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.

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.

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.