Much of the eastern United States was lashed with intense storms on Monday, leaving at least two people dead in Alabama and South Carolina, hundreds of thousands without power and thousands of flights canceled or delayed.

Millions of people were under severe weather alerts, including tornado watches, as rain, strong winds and hail swept east along nearly the entire eastern seaboard, from Alabama to New York.

The National Weather Service (NWS) had predicted a "moderate risk" of hazardous storms, with gusts up to 130 kilometers per hour.

"Stay weather aware and make sure you have multiple ways to receive warnings," the NWS in Baltimore and Washington said on social media earlier in the day.

As much of the severe weather danger subsided into the late evening, some areas faced flood threats as rain continued to fall.

By early Tuesday, nearly 600,000 customers were without power along the East Coast, from Pennsylvania to Georgia, according to tracking website PowerOutage.us.

Local media and government agencies in Maryland released images of downed power lines strewn across streets, and trees that fell into homes and across roads and rail lines.

Other southern states experienced similar storm damage, with Georgia Power releasing photos of fallen trees that pulled down power lines due to high winds, hail and heavy rain.

"Our crews are working safely and as quickly as possible to get the lights back on," the electric utility said on X, formerly known as Twitter.

More than 1,700 U.S. flights were canceled on Monday and more than 8,000 delayed as the severe weather loomed, website FlightAware said.

In Washington, federal agencies sent employees home early at 3:00 pm on Monday in anticipation of the weather.

The storms came as large parts of the southern United States, including Texas, Louisiana and Florida boiled under excessive heat warnings, with temperatures up to 42 Celsius predicted through Tuesday.

Scientists say climate change has amplified the intensity and frequency of extreme weather events around the world.

(With input from AFP)