More than 300,000 homes and businesses were without power on Tuesday morning after powerful thunderstorms lashed across the US East Coast.
Tornado watches and warnings have been posted in 10 states, from Tennessee in the south to New York in the north. The National Weather Service also issued a rare tornado watch for Washington, warning of a “significant threat of damaging and locally destructive hurricane-force winds”.
Two fatalities have been reported so far, including a 15-year-old boy in the town of Anderson, South Carolina. The town's coroner said the boy was killed when a large tree uprooted during the storm and landed on him.
In Florence, Alabama, police said a 28-year-old man was killed after being struck by lightning, local media reported.
Nearly 1,800 US flights had been cancelled by Monday night and an additional 8,883 were delayed, according to tracker FlightAware.
The storms also caused President Joe Biden to move up his planned departure from Washington to the south-western US. The Office of Personnel Management also closed federal offices earlier than anticipated to prepare for the storm.
In total, more than 1.1 million homes and business were without power on Monday evening. The vast majority of power cuts took place in states along the storms' path.
As of Tuesday morning, nearly 350,000 homes were still without power, according to tracker PowerOutage. A Tennessee utilities company said its 8,000 customers without power may have to wait for an extended amount of time before it returns.
“Because of the widespread and severe nature of the damage remaining, we expect repair work to span multiple days,” the Knoxville Utilities Board said in a tweet.
The storm system arrived as much of the southern US continues to experience record-breaking heat. This includes the desert south-west, where Mr Biden is scheduled to deliver remarks on climate conservation efforts on Tuesday.
The Southern Plains, Gulf Coast and Florida will also continue to feel the prolonged heatwave.
“Much of this region has seen record high maximum temperatures and record high morning low temperatures over the past several days, and the potential for additional records will continue through much of week,” the NWS said in its Tuesday bulletin.
Scientists have claimed that climate change and global warming are major contributors to the extreme weather events and intense heat being felt across the world.