Matthew whipped North Carolina on Sunday morning, causing "record-breaking" flooding and blowing powerful winds after killing 10 people in three states.
Hurricane Matthew killed at least three people in North Carolina, four in Florida and three in Georgia, authorities said Saturday.
After making landfall as a Category 1 hurricane in South Carolina on Saturday, the National Hurricane Center said Matthew was no longer a hurricane early Sunday and is now considered a post-tropical cyclone.
Despite its new title, it's still packing maximum sustained winds of 75 mph (120 kph) -- the same as a Category 1 hurricane, forecasters said.
Matthew's only change is in its "core structure," hence the change to a cyclone, CNN meteorologist Allison Chinchar said. However, she warned, the change in name does not mean it's any less dangerous.
"It's still packing the same hurricane-force winds and potential for flooding and is still as deadly as a hurricane," she said.
Post-tropical cyclone Matthew is expected to pound eastern North Carolina with torrential rains until later Sunday.
Hundreds dead in Haiti
After a destructive trip through the Caribbean that left hundreds dead in Haiti, Matthew knocked out power to millions of people Saturday night and toppled trees along parts of the US Southeast -- from Florida to the Carolinas.
Not out of the woods
North Carolina Gov. Pat McCrory warned residents the flooding could be the worst since Hurricane Floyd pounded the state in 1999.
Even though Matthew made its first US landfall Saturday in South Carolina, part of the storm's eyewall -- the hurricane's strongest section -- passed over coastal Florida, Georgia and South Carolina from Friday into Saturday, flooding low-lying areas, downing trees and making some roads impassable.
The storm killed hundreds in the Caribbean, almost entirely in Haiti. More than 330 people died in Haiti, according to the nation's Civil Protection Service.
Others reported much higher deaths. A count by Reuters, based on information from local civil protection officials, puts the death toll in Haiti well over 800. Four deaths were reported in the Dominican Republic and one in St. Vincent and the Grenadines.
Flooding in Georgia, South Carolina
The storm left more than 2 million utility customers without power Saturday night in South Carolina (833,000), Florida (673,000), North Carolina (457,000) and Georgia (276,000).
In the coastal Georgia city of Savannah, Sue Alice Walker, 85, said she was sleeping in her house when she awoke to find 3 inches of water flowing inside.
"First I saw it in the living room, then in the kitchen, and then last it came in my son's room," she told CNN's Sara Ganim, adding that she spent the rest of the night and much of Saturday morning mopping and shoveling the water into buckets.
Storm surges sent water spilling into Myrtle Beach's streets Saturday before the storm's center arrived, video posted by CNN affiliate WPDE showed.
"I'm going to ask for patience. ... Do not plan to go home," Haley said, asserting that driving conditions weren't safe.
Florida left drenched
In Florida, Matthew left a trail of destruction.
Water from the storm rushed through streets, making roadways look more like rivers in parts of Jacksonville, Merritt Island, Fleming Island and other Florida communities.
Florida struggled with the rising water, rain and strong winds as meteorologists said the storm surge was more than 4 feet in some areas.
Jacksonville was not battered as heavily as initially feared. But several communities nearby received extensive damage with water surging down some streets, and massive trees toppled over.
Part of the Jacksonville Beach Pier washed away Friday morning, according to CNN affiliate WFOX/WJAX. The original pier was washed away during Hurricane Floyd and rebuilt a few years later, the station said.