At least one person was killed in the storm, two others were hospitalized, and a gas leak forced authorities to evacuated part of Stratford, a town of about 746 residents 50 miles northwest of Des Moines.
"Half the town's gone," said Bob Smith, who has lived in Stratford for 12 years. He said he ran from his camper as the tornado touched down.
Search teams later found the body of another Stratford resident, Lucille Runyan, 80. Her daughter-in-law said Runyan's son had been with the team that discovered her. Another woman was pulled alive from the rubble, searcher Scott Bergman said. Authorities said at least two dozen homes in the town were destroyed.
In Woodward, 30 miles to the south, 20 to 40 homes were severely damaged, Dallas County Sheriff Brian Gilbert. He said emergency crews had searched house-to-house and hadn't found any victims by evening.
"The big problem right now is power lines are down and gas lines are ruptured," Gilbert said. "We are encouraging people to stay out of the area."
National Weather Service meteorologist Craig Cogil said it appeared that at least three tornadoes touched down Saturday afternoon.
In Ames, football fans gathering for the Iowa State-Colorado game were cleared from the stands and told to take shelter in the nearby basketball arena as the tornado sirens sounded. The storm hit on the edge of the city, where city spokeswoman Susan Gwiasda said the damage was mostly broken windows and downed power lines.
"We dodged a bullet with the track of that storm," Iowa State University spokesman John McCarroll said. He said officials had prepared for the chance of dangerous weather during the game.