The storms also brought hail, some of it the size of a golf ball, the Denver Post reported. Funnel clouds were spotted in several places.

Jim Kalina, a meteorologist with the National Weather Service, said the agency received 10 reports of tornadoes touching down. He said some could have involved the same tornado.

Tornadoes are common in Colorado at this time of year, he said.

"We don't usually see them destroying a couple of towns and a tornado that is three-quarters of a mile wide," Kalina said. "That is unusual for here."

The Weld County coroner's office said one death had been reported, but provided no details on the circumstances.

In Windsor, schools were locked down and parents warned to stay away. Children from a daycare center were taken to a bank building not long before their own building was damaged by the storm.

Windsor and Greeley both suffered heavy damage.

"It passed right over us like a big, white monster," Thomas Coupe, 87, of Windsor, told the Greeley Tribune.