Tropical Storm Isaias has hit the US east coast with maximum sustained winds of 140km/h, according to the US national hurricane service (NHC).
The tropical storm was downgraded from a Category 1 hurricane after it made landfall near Ocean Isle Beach in the state of North Carolina, just after 11pm on Monday.
The NHC has warned inhabitants in affected areas of possible "life-threatening" storm surges, flooding and "dangerous winds."
The NHC said the tropical storm was moving along eastern North Carolina with winds of up to 87km/h and gusts of up to 111km/h.
Early on Tuesday, streets and shops were flooded in the tourist city of Myrtle Beach in North Carolina, the Washington Post reported.
The tropical storm was expected to ease on Tuesday over North Carolina and move further northeast near the coast.
Warnings were issued for several cities further along the US coast, including Washington, Philadelphia and New York, with barriers erected in parts of Manhattan, CNN reported. Power outages were expected.
New Jersey Governor Ryan Murphy announced a statewide state of emergency, shutting down all state offices and advising people not to drive.
Isaias had passed over parts of the Bahamas as a hurricane on Saturday, but weakened again into a tropical storm on its way towards the east coast of Florida. The storm did not hit land in Florida, despite initial predictions it would.
Australian Associated Press