Tropical Storm Ophelia is moving inland across North Carolina, lashing coastal areas with rain, damaging winds and dangerous surges of water, the United States hurricane centre says.
Life-threatening flooding was forecast for parts of eastern North Carolina and southeastern Virginia, with the system expected to weaken after landfall.
Radar, hurricane hunter aircraft and observers on the ground found Ophelia's centre came ashore early Saturday near Emerald Isle with maximum sustained winds of 110km/h, the hurricane centre said.
An update at 8am put the storm's centre about 64km northwest of Cape Lookout, weakening slightly with maximum winds dipping to about 105km/h.
Ophelia was likely to turn north later on Saturday and then shift northeast on Sunday, the hurricane centre said.
The storm promised a weekend of windy conditions and heavy rain up to 18cm in parts of North Carolina and Virginia, as well as five to 10cm in the rest of the mid-Atlantic region through Sunday.
A storm surge warning, indicating danger from rising ocean water pushed inland by Ophelia, was in effect from Bogue Inlet, North Carolina, to Chincoteague, Virginia.
Surges of between 1.2 to 1.8 metres were forecast in some areas.
A tropical storm warning was issued from Cape Fear, North Carolina, to Fenwick Island, Delaware.
The centre ended its hurricane watch advisory in parts of coastal North Carolina.
The governors of North Carolina, Virginia and Maryland declared a state of emergency on Friday.
Some schools closed early and several weekend events were cancelled, while in Washington, the Nationals baseball team postponed its Saturday game.
North Carolina Governor Roy Cooper issued the declaration to help expedite preparations and provide a swift response.
"We want to ensure that farmers, first responders and utility crews have the tools necessary to prepare for severe weather," Cooper said.
The North Carolina Ferry System suspended service on all routes until conditions improved.
Virginia Governor Glenn Youngkin said the emergency declaration aimed "to ensure that all communities, particularly those with the greatest anticipated impact, have the resources they need".
He encouraged residents to prepare emergency kits and follow weather forecasts closely.
Maryland Governor Wes Moore said the state expected an extended period of strong winds, heavy rainfall and elevated tides.
It is not uncommon for one or two tropical storms, or even hurricanes, to develop right off the East Coast each year, hurricane centre director Michael Brennan said.
"We're right at the peak of hurricane season," he said.
"We can basically have storms form anywhere across much of the Atlantic basin."
Scientists say climate change could result in hurricanes expanding their reach into mid-latitude regions more often, making storms like this month's Hurricane Lee more common.
Australian Associated Press