700,000 without power as storms batter US Midwest

First responders and utility crews worked overnight into Wednesday clearing roads from trees and wires that were downed during severe storms in the Midwest that unleashed tornadoes, heavy rains and flash flooding while knocking out power to hundreds of thousands of customers.

A 4-year-old boy was killed when a tree fell on a home in Geneva, Indiana, during Tuesday's storms, the Jennings County Sheriff's Office said.

In Ohio, Governor Mike DeWine said a resident of Roseville died during a health emergency when first responders, faced with flooded roads, couldn't reach them. Officials in Portage, Indiana, were investigating whether the severe weather played a role in a reported house explosion that killed a person.

Lightning struck a prison complex southwest of Cleveland on Tuesday, injuring 16 incarcerated people who were hospitalised, according to the Ohio Department of Corrections. Their conditions weren't immediately known.

The storms inflicted a wide swath of damage from the Chicago area to western Pennsylvania, and the National Weather Service said threats of severe thunderstorms and heavy rainfall will continue over the next few days in the Midwest, Ohio Valley and central Appalachians.

More than 700,000 customers were without power on Wednesday morning in Illinois, Indiana, Ohio, Kentucky and West Virginia, according to poweroutage.us.

The National Weather Service said it confirmed three tornadoes in counties south of Chicago.

Water rescues were reported during heavy rains in several states including Ohio, where DeWine sent 40 Ohio Army National Guard members to help in two counties east of Columbus.

Tornado warning sirens howled Tuesday as the skies darkened in the Chicago area. All flights were temporarily stopped at Chicago's two major airports, and officials warned of delays as the backlog was cleared.

Photos posted on social media from the Chicago area and across the state line in Indiana showed flooded roads, trees tangled in power lines and homes with gashes in their roofs.

"No power. It was very scary. We were down in the basement," said Javid Jenkins of Homewood, a Chicago suburb. "We're built for snow. We're built for cold. We're not built for this."

Jenkins, 54, said he was driving around for gas to fire up a generator to preserve food in his refrigerator.

Forecasters said a wind gust of 159 kph was recorded in Gary, Indiana.

Elsewhere there were numerous reports of gusts of 128 kph or more at personal weather stations.

Preliminary information indicated that the intense system that swept from Iowa into Indiana over several hours qualified as a derecho, the weather service's Storm Prediction Center said on Tuesday evening.

Derechos are prolonged straight-line wind events that unleash heavy rainfall and travel far distances.

The damage they cause is sometimes comparable to the destructive forces of tornadoes or hurricanes.

"Total devastation. No roof," said Kerry Hourigan, standing outside her home of 25 years in Tinley Park, another Chicago suburb.

"Stupid thing, but my focus was I just bought a new barbecue grill, and I have no idea where that is. It's disappeared."

Agencies