WASHINGTON, Ill. — As a powerful tornado bore down on their Illinois farmhouse, Curt Zehr’s wife and adult son didn’t have time to do anything but scramble down the stairs into their basement.

Uninjured, the pair looked out moments later to find the house gone and the sun out “right on top” of them, Zehr said. Their home, on the outskirts of Washington, Ill., was swept up and scattered over hundreds of yards by one of the dozens of tornadoes and intense thunderstorms that swept across the Midwest on Sunday, leaving at least six people dead and unleashing powerful winds that flattened entire neighborhoods, flipped over cars and uprooted trees.

“They saw (the tornado) right there and got in the basement,” said a stunned Zehr, pointing to the farm field near the rubble that had been his home.

Early Monday, Washington Mayor Gary Manier estimated that from 250 to 500 homes were either damaged or destroyed in the storm and that it wasn’t clear when residents would be allowed to return.

“Everybody’s without power, but some people are without everything,” Manier told reporters in the parking lot of a destroyed auto parts store and near a row of flattened homes.

“How people survived is beyond me,” he said.

The unusually powerful late-season wave of thunderstorms brought damaging winds and tornadoes to 12 states: Michigan, Wisconsin, Iowa, Illinois, Missouri, Indiana, Ohio, Kentucky, Tennessee, West Virginia, Pennsylvania and western New York.

Bill Bunting, forecast operations chief of the National Weather Service’s Storm Prediction Center in Norman, Okla., said the storms all belonged to the same system and would be “moving rapidly to the east and continue east overnight and into the morning.”

Illinois was the hardest struck with at least six people killed and dozens more injured.

An 80-year-old man and his 78-year-old sister were killed by a tornado that hit their farmhouse near the rural southern Illinois community of New Minden, coroner Mark Styninger said. A third person died in Washington, while three others perished in Massac County in the far southern part of the state, said Patti Thompson of the Illinois Emergency Management Agency. She did not provide details.

Communications remained difficult and with many roads impassable it was not clear if the injury and death tolls would rise on Monday. Ill. Gov. Pat Quinn declared seven counties disaster areas.

Washington, a town of 16,000 about 140 miles southwest of Chicago, appeared to have suffered the most severe damage. The tornado cut a path about an eighth of a mile wide from one side of town to the other, State Trooper Dustin Pierce said.