CHARLESTON — Hurricane Matthew weakened to a Category 1 storm on Saturday, but packed a strong enough punch to down trees and deliver a six-foot storm surge and severe flooding to historic downtown Charleston.

Matthew officially made landfall Saturday morning. It made landfall over the Cape Romain National Wildlife Refuge near McClellanville, S.C., which is 40 miles northeast of Charleston, the National Hurricane Center said.

As of 11 a.m. the center of Matthew is 55 miles south-southeast of Myrtle Beach, S.C., and the hurricane is moving to the northeast at 12 mph.

Hurricane warnings remain for the entire coastline of South Carolina and portions of the Georgia and North Carolina coasts.

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Matthew is barely maintaining hurricane strength, as the storm's winds have decreased to 75 mph, just 1 mph above tropical storm level.

South Carolina governor Nikki Haley said Saturday that 437,000 people were without power in the state. She also pleaded with residents driven out of their homes not to rush back in immediately.

“The one thing I do want to say is that now is when the frustration comes,” Haley told reporters. She said residents will want to get back to their home quickly, but warned that "most fatalities occur after the storm because people move back too soon.”

At 8 a.m. ET, Matthew was located 20 miles south southeast of Charleston, moving at 12 mph, the National Hurricane Center said in its advisory, packing sustained winds of up to 85 mph, almost 11 mph below Category 2 status.. The storm is expected to reach southern North Carolina by nightfall.

At least four people died in Florida and more than 1.1 million people were without power. An elderly St. Lucie County couple died from carbon monoxide fumes while running a generator in their garage and two women were killed in separate events when trees fell on a home and a camper.

In Charleston, as the storm churned closer, the water level at low tide as six feet above normal, according to the National Weather Service in Charleston and Mayor John Tecklenburg warned that the biggest danger would come at high tide around 1 p.m. ET.

He tells CNN that the city is expecting "severe flooding" in the coastal city as the storm surge crests.

The historic downtown area normally abuzz with weekend tourist traffic at bars and restaurants was eerily quiet as residents and visitors heeded a midnight-to-6 a.m. curfew Many stores and shops boarded up with plywood and protected by stacks of sandbags.

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Most of downtown Charleston’s hospital district was surrounded by floodwaters, with the prominent Calhoun Street knee to hip deep in some spots, The Post and Courier reports. The newspaper also noted that exploding transformers echoed could be heard as the wind picked up.

At one point, in the height of the storm, EMS service was suspended in Charleston County after authorities declared bridges unsafe for travel.

As the storm hammered the city, the Charleston County EMS suspended service, declaring a condition red as bridges became unsafe for travel.

“We do not want to deal with individuals who get themselves trapped out in this severe situation,” Chief Greg Mullen said.

At least 18 roads in the city of Mount Pleasant, S.C., are impassable, officials say. Charleston County authorities reported trees and power lines down throughout the county as 1,538 people waited out the storm in shelters.

As of 6 a.m. Saturday, more than 125,000 power outages were reported by utilities operating in the Low Country as a result of Hurricane Matthew. South Carolina Electric & Gas Company reported a total of 105,404 outages statewide, while South Carolina's Berkeley County Electric Cooperative reported 20,114.

Of the 500,000 people instructed to leave low-lying coastal areas, Haley said that more than 300,000 people had pulled out. Many of those who didn't, she said, were on Daniel Island, a 4,000-acre area on the east bank of the Cooper River in Charleston.

Strong winds from Matthew's eyewall also slammed into downtown Savannah early Saturday, downing trees and sending street signs flying. As the sun began to rise over the 283-year-old city, floodwaters inched steadily higher. Police reported numerous downed trees and washed out roads.

Tim Smith, of The Greenville News, is reporting from Charleston.