Most of the severe weather from Tuesday night stayed south and east of the Sioux City area.
The fire department lost power in Missouri Valley, where fallen power lines and lightning touched off fires.
The Iowa State Patrol says the high winds knocked over some semitrailers on Interstate 29.
MidAmerican Energy said Wednesday morning that nearly 6,600 of its Iowa customers had no power, including nearly 6,100 in Fort Dodge.
Several downed trees littered yards and streets in Council Bluffs.
Winds of up to 70 mph were reported in Carroll and Shelby counties, and golf ball-size hail was reported in Crawford County.
AP contributed to this story