Tornadoes and devastating thunderstorms have left nearly 300,000 residents across seven states without power as of Monday night.
Over the weekend, huge storms killed at least 23 people and left a path of destruction across the central US.
Forecasters said the greatest weather risk has shifted east, covering a broad sweep of the country from Alabama to New York.
More thunderstorms, damaging wind gusts, hail and flash flooding are expected.
Worst day this year
Heavy rain is expected to batter the east coast into Tuesday morning, including parts of New York, Pennsylvania, New Jersey and Maryland, said the National Weather Service (NWS).
This excessive rain will bring with it a slight risk of severe thunderstorms developing over parts of the northeast to the southeast of the US, the agency added.
The NWS has also forecast that severe thunderstorms could develop over Texas on Tuesday, where wind gusts could reach 120 km/h or greater.
Searing heat will also continued in parts of the US south, with record or near-record high temperatures expected.
On Monday morning, more than 120 million Americans woke to severe weather warnings.
Sunday was the busiest severe weather day in the US so far this year, with more than 600 reports of storm damage across 20 states. Twisters and heavy winds reduced buildings to piles of rubble, flipped cars and brought down power lines.
Lightning, thunder and heavy rain meanwhile forced the evacuation of around 125,000 spectators as Sunday’s Indianapolis 500 race was delayed by four hours.
Weather deaths were reported in several states, including eight in Arkansas, seven in Texas, two in Oklahoma and five in Kentucky. In Alabama, a 79-year-old woman was killed on Monday morning after a tree fell into her home, local media said.
President Joe Biden spoke with the governors of each state affected by the storms, and offered federal assistance.
On Monday, Kentucky Governor Andy Bashear declared a state of emergency after storms pummelled much of the state.
“Last night many families and communities were not safe,” he said. “We had devastating storms that hit almost the entire state.”
In Colorado, a farmer and 34 of his cows were killed in a lightning strike.
In Texas, Governor Greg Abbott said more than a third of counties were subject to a disaster declaration after extreme weather ploughed through the state.
All of the state’s seven deaths were reported in Valley View in Cooke County, Texas near the Oklahoma border after a tornado hit a rural area near a mobile home park.
Two children, aged two and five, and three members of the same family were among those found dead.
Footage from the area showed a filling station and rest stop almost completely destroyed, with twisted metal littered over damaged vehicles.
The latest twisters follow another powerful tornado which tore through a rural Iowa town and killed four people earlier in May.
Government forecasters have also described this summer as a possibly “extraordinary” 2024 Atlantic hurricane season, beginning next month.