Millions are sweltering in the aftermath of violent storms that pummelled the eastern United States, killing at least 13 people and leaving three million without power during a heat wave.
Power officials said on Sunday the outages wouldn't be repaired for several days to a week, likening the damage to a serious hurricane.
Emergencies were declared in Maryland, West Virginia, Ohio, the District of Columbia and Virginia, where Governor Bob McDonnell said the state had its largest non-hurricane outage in history, as more storms threatened.
"This is a very dangerous situation," the governor said.
In West Virginia, 232 Amtrak passengers spent Friday night on a train that was blocked on both sides by trees that fell on the tracks, and they were waiting for buses to pick them up Saturday.
In Illinois, storm damage forced the transfer of dozens of maximum-security, mentally ill prisoners from one prison to another.
In some Virginia suburbs of Washington, emergency call centres were out of service, with some residents told to call local police and fire departments.
Huge trees fell across streets in Washington, leaving cars crunched up next to them, and onto the fairway at the AT&T National golf tournament in Maryland.
Mobile phone and internet service was spotty, gas stations shut down and residents were urged to conserve water until sewage plants returned to power.
The outages were especially dangerous because they left the region without air conditioning in an oppressive heat.
Temperatures soared to highs in the mid-40s in Baltimore and Washington, where it had hit 40 celsius on Friday.
The storm did damage from Indiana to New Jersey, although the bulk of it was in West Virginia, Washington and suburban Virginia and Maryland.
At least six of the dead were killed in Virginia, including a 90-year-old woman asleep in bed when a tree slammed into her home.
Two young cousins in New Jersey were killed when a tree fell on their tent while camping. Two were killed in Maryland, one in Ohio, one in Kentucky and one in Washington.
Illinois corrections officials transferred 78 inmates from a prison in Dixon to the Pontiac Correctional Centre after storms Friday night caused significant damage, Department of Corrections spokeswoman Stacey Solano said.