Ms. Elder said winds blew over trees, flipped cars, downed power lines, ripped up road signs, and tore roofs off buildings, some of which caught fire.
The weather service also confirmed two tornadoes in southern Wisconsin and two in northern in, including an EF-1 that swept the rural community of Wakarusa, about 25 miles (40 kilometers) southeast of South Bend.
Alliant Energy said that about 140,000 customers in Iowa remained without power, more than half of them in Cedar Rapids.
MidAmerican Energy said almost 101,000 customers in the Des Moines area were without power after the storm moved through the area.
Omaha Public Power District reported more than 55,500 customers without power in Omaha and surrounding communities.
"We believe that we will be able to substantially restore power in Cedar Rapids in the next five to seven days", Wagner said at an afternoon news conference with city leaders. Meanwhile, demand for gas to fuel generators, chainsaws and vehicles has spiked, leading to long lines at stores that sell gas.
The storm caused extensive crop damage in the nation's No. 1 corn-producing state as it tore across Iowa's center from west to east.
Iowa Secretary of Agriculture Mike Naig said Tuesday that about 10 million acres of Iowa's almost 31 million acres of agricultural land sustained damage.
Farmers reported that some grain bins were destroyed and fields were flattened, but the extent of damage to Iowa's agriculture industry wasn't immediately clear.
The only known death in Iowa was a 63-year-old bicyclist who was hit by one of several large trees that fell on a bike path outside Cedar Rapids.
Poweshiek County Sheriff Thomas Kriegel says a 42-year-old woman sitting on her porch in Malcom on Monday was struck by a large tree blown over as the storm moved through, and a 41-year-old electrician who worked for the city of Brooklyn died when he was electrocuted by a power line he was reconnecting. Minutes later he headed to his basement for safety as the storm took aim at Chicago, starting with its suburbs.
"We have damage to homes and businesses, including siding and roofs damaged", he said. She said pictures fell off the wall, water seeped in through windows and she anxious the glass would blow in and injure her. "Very high winds. It will be a significant effort to get through it all and get everybody back on", she said. A local utility official told Mathis on Wednesday that it could be a week before everyone has power restored.