State and local officials warned residents to prepare for the storms and possible power outages. Power companies said they were preparing for storm response.
Storms with swift, straight-line winds soaked parts of Ohio, damaging trees and barns and leaving many without power early Thursday as commuters dodged fallen branches on roads and faced backups at intersections where traffic lights were out.
Straight-line winds topping 70 mph were reported and more than two dozen tornado warnings were issued as two rounds of storms pummeled the state, but no twisters have been confirmed, said Phillip Johnson, who was part of the team monitoring developments for the Ohio Emergency Management Agency.
In New Jersey, officials opened the soaked state's Emergency Operations Center on Thursday morning to monitor the storm's progress. The National Weather Service issued a flood watch for most of the state. Forecasters predicted 1 to 2 inches of rain will fall on swollen rivers and streams.
By early Thursday, a derecho hadn't developed. And Greg Carbin of the National Weather Service's Storm Prediction Center in Norman, Okla., said, "With each hour that goes by, it's less likely."
While the Midwest dodged a derecho, several tornadoes, large hail and flooding did some damage.
In the small town of Belmond, Iowa, about 90 miles north of Des Moines, Duwayne Abel, owner of Cattleman's Steaks & Provisions restaurant, said a tornado demolished part of the building. No one was in the restaurant at the time.
"I was, oh, 8 miles west of town and I looked toward town and I could see a funnel cloud, having no idea it was exactly where our restaurant was," Abel said. His wife and an employee were able to get out of the restaurant and sought shelter in a basement.
In Iowa, at least two businesses and a home were damaged, authorities said. A storm ripped through a farm in rural Alexander, destroying a motor home. Tens of thousands of people across the Upper Midwest lost power.
In Wisconsin, authorities said thunderstorms packing heavy rain and high winds caused a Wal-Mart roof to partially collapse. Lake Delton Fire Chief Darren Jorgenson says two employees had minor injuries, but no customers were hurt.
"We're just happy that we don't have reports of injuries or fatalities," said Stephanie Bond with Iowa Homeland Security and Emergency Management. "We just hope the extent of the damage is minimal."
Even before the storms moved through, officials postponed Wednesday night's Chicago White Sox game against the Toronto Blue Jays and canceled a symphony concert at the city's downtown Millennium Park. The Metra commuter rail system temporarily halted service, and Northwestern University canceled classes and finals at its campuses in Chicago and suburban Evanston. Airlines canceled more than 120 flights at O'Hare International Airport.
Pennsylvania Emergency Management Agency spokesman Cory Angell said a standby worker was added at the emergency operations center in Harrisburg and officials had ensured two National Guard helicopters were ready if needed for water rescues.
Last year, a derecho caused at least $1 billion in damage from Chicago to Washington, killing 13 people and leaving more than 4 million people without power, according to the weather service. Winds reached nearly 100 mph in some places. In addition to the people who killed in the storm, 34 more people died from the heat wave that followed in areas without power.
For Washington, Philadelphia and parts of the Mid-Atlantic the big storm risk continues and even increases a bit Thursday, according to the weather service. In Washington, the Office of Personnel Management said federal agencies in the area would open but that workers would be allowed to take unscheduled leave or work from home.
The term derecho was coined in 1888, said Ken Pryor, a research meteorologist at the Center for Satellite Applications and Research at the National Oceanic and Atmospheric Administration in College Park, Md. The word is Spanish for "straight ahead" or "direct," Pryor said.
The structure of a derecho-producing storm looks distinctive in radar and satellite imagery, Pryor said. "The systems are very large and have signatures that are very extreme," he said. "You get large areas of very cold cloud tops that you typically wouldn't see with an ordinary thunderstorm complex. The storms take on a comma or a bow shape that's very distinctive."