Jennifer Pickering told CNN the storm that flattened cornfields sounded like a train and felt like it took the breath out of her body.
Boards from other buildings were blown into her brother's house, where she was staying, she said. Broken windows and howling rain pressurized the home so much they could not open doors, and she found her sister-in-law in bed covered in sheets of broken glass with boards flying around her.
"I honestly thought at times we were going to die," Pickering said.
The storm system is classified as a derecho, and it has far exceeded the criteria of winds in excess of 58 mph and damage spanning at least 250 miles, CNN meteorologist Tyler Mauldin said.
Winds reached 100 mph as the storms moved through Iowa and Illinois. More than a million customers in the two states were without power Monday night, according to PowerOutages.us.
A total number of injuries has not been reported, but more than 450 storm reports were made -- 95% of which were wind reports.
Those numbers are expected to go up as the storms, though considerably weakened, push southeast, Mauldin said.
Storm damage prompts curfew in Cedar Rapids
Cedar Rapids, Iowa -- where the NWS reported wind gusts over 90 mph -- enacted an overnight curfew because of the damage left behind.
"There is devastating property damage to homes and businesses in all parts of the city," the city government wrote in an advisory to residents Monday. "Trees and power lines are down throughout the city, making many major roads impassable."
The curfew will be in place from 10:00 p.m. to 6:00 a.m. until further notice, and local transit service in the city has been suspended through Wednesday.
About 50 people were hospitalized with storm-related injuries around Cedar Rapids, according to the police department, and electrocution from downed powerlines continues to be the main concern.
A 'particularly dangerous situation'
The storms are part of what the National Weather Service's Storm Prediction Center called a "particularly dangerous situation."
A derecho can produce destruction similar to that of a tornado, but the damage typically occurs in one direction along a relatively straight swath. The term "straight-line wind damage" sometimes is used to describe derecho damage, said the SPC.
Toppled powerlines sparked numerous fires, the Chicago Fire Department tweeted Monday afternoon. And according to a tweet from the National Weather Service in Chicago, powerlines blocking roadways, downed trees and debris can be seen across much of northern Illinois.
Outside of Iowa City, a family came to the aid of the driver of a semi-truck they said had blown over on Interstate 80.
Michelle Turney told CNN she, her husband and her son helped the driver out of the truck and kept him in their pickup while they waited for paramedics and police. Her husband kept the man talking to help him relax, she said.
CNN's Judson Jones, Amanda Jackson and Andy Rose contributed to this report.
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