Some two million people are without power after violent storms hit the region around the US capital, Washington DC.
The storms swept from the Midwest states to the region around Washington, packing winds of up to 80mph (130 km/h).
The power outages left many sweltering without air conditioning amid a record-breaking heatwave.
At least five deaths have been linked to the storm.
The storm is locally referred to as a "derecho" - a violent, straight-lined windstorm associated with a fast-moving band of severe thunderstorms.
It left behind felled trees, streets littered with fallen branches and downed power lines.
Washington's transit authority said most metro lines were back to normal service after the storm disrupted service on all lines during Friday night. But many Metrobus routes were subject to detours or delay due to downed trees and power lines.
Amtrak suspended services from Washington to Philadelphia until at least mid-morning on Saturday, Associated Press reported.
Meanwhile, a heatwave which has seen all-time records smashed with temperatures of 104F (40C) in DC, was set to continue, said the National Weather Service - and it warned that another round of severe weather
The storms started in the Midwest and moved quickly eastward, hitting the mid-Atlantic states on Friday evening.
As well as gusty winds, users of the social network site Twitter reported spectacular, sustained displays of lightning. There were also reports of hail the size of a US quarter coin - just under an inch (2.4mm).
The storms left more than two million people without power, reported Associated Press, which said that a state of emergency had been declared in West Virginia where more than 500,000 were hit by power cuts.
Power companies said they were working hard to restore power to customers, but Pepco and Baltimore Gas and Electric (BGE) were among those warning that it could be days before all services were reconnected.
Meanwhile, the Washington Suburban Sanitary Commission imposed mandatory water restrictions for all customers in Montgomery and Prince George counties because the storms cut power to two water filtration plants and other facilities.
It asked customers to stop all outside water use and restrict water use at home.
At least five deaths have been attributed to the storms.
In Springfield, Virginia, a 90-year-old woman died when a tree fell on her home, AP quoted police as saying. Also in Springfield, a 27-year-old man died when a tree fell on his car.
And a 25-year-old man died in Anne Arundel county, Maryland, when a tree hit his car, reported the Baltimore Sun news site.
The US National Weather Service warned people in the region to alert to the latest weather warnings on Saturday.
"Another round of severe weather will develop across the Ohio Valley and track into the northern Mid-Atlantic states, where damaging winds will be the primary threat," it said on its website.
"At this time, it appears the greatest risk will stretch from southern Ohio into Maryland and northern Virginia."