Wind up to 67 mph ripped off roofs, knocked over trucks and outbuildings and blacked out thousands of customers as thunderstorms rumbled through Minnesota and Iowa.

Emergency crews had to rescue a man whose tractor-trailer rig was blown over at the central Iowa town of Nevada, just east of Ames, said Rob DeRoy of the National Weather Service (search). Part of the roof of the town's high school was torn off.

"With winds up to 70 mph, it's going to do some damage to something," DeRoy said of Monday's storms.

South of Lake Crystal in southern Minnesota, the wind toppled a 15,000 bushel grain bin at Inez Rollings' farm. "I heard this whoop," she said. "I looked out the window and saw the grain bin was gone."

Boats were overturned on Lake Calhoun in Minneapolis and Gray's Lake in Des Moines, Iowa, tree limbs were snapped and siding was torn from houses in some areas.

Hail nearly 2 inches in diameter was reported in Minnesota's Ramsey County, which includes St. Paul.

Takeoffs and landings were halted briefly during the afternoon storms at Minneapolis-St. Paul International Airport, said airports commission spokesman Patrick Hogan.

About 35,600 Xcel Energy (search) customers lost power in the Minneapolis-St. Paul area and more than 4,000 MidAmerican Energy (search) customers were blacked out in central Iowa.

On Sunday, thunderstorms caused scattered damage in North Dakota, producing wind up to 103 mph at Hampden.