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Hurricane Matthew's eyewall whipped parts of Florida's northeast coast Friday afternoon, marching up the southeastern United States after its deadly spree across the Caribbean.

Three deaths in Florida may be tied to the hurricane, officials said. The storm weakened to a Category 3 hurricane overnight after decimating Haiti, where the death toll rose Friday to more than 800, according to Reuters. NBC News could not immediately confirm that number.

The hurricane weakened to a Category 2 by Friday evening. Despite weakening, Matthew still packed maximum sustained winds of 110 mph Friday afternoon, hammering the Florida shoreline with heavy rain and high winds. More than one million customers were without power, the Florida's Public Service Commission tweeted.

In St. Augustine, Florida, streets were flooded. Businesses were all shuttered, and open gas stations were nearly impossible to find. Abandoned cars were parked in the middle of residential streets, while broken tree branches and toppled garbage containers floated by.

The storm was about 55 miles east-northeast of Jacksonville and 105 miles south-southeast of Savannah, Georgia, as of 8 p.m. ET, and the storm was moving north at 12 mph, the National Hurricane Center said.

Hurricane warnings were in effect from north of the Flagler-Volusia county line to Surf City, North Carolina.

Jacksonville was among the places under a hurricane warning — its first such warning in 17 years, according to The Weather Channel.

LIVE BLOG: The Latest on Hurricane Matthew

President Barack Obama declared a state of emergency in North Carolina Friday afternoon, making it the fourth state after Florida, Georgia, and South Carolina to receive the designation for the storm.

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In a news conference, North Carolina Gov. Pat McCrory said the state was likely to see a “major impact” from the storm — and possibly its worst flooding since Hurricane Floyd in 1999. Some parts of the coast were expecting more than a foot of rain, storms surges of six feet and winds as powerful as 60 miles per hour, McCrory said.

Three deaths in Florida could be related to the hurricane, officials said. A woman was killed by a falling tree in Volusia County as she went outside to feed her animals — possibly while the eye of the hurricane created a deceptive break in the weather — and a woman in her 50s in St. Lucie County died after suffering a cardiac arrest overnight after emergency personnel stopped operations due to wind gusts, authorities said.

Friday afternoon a tree fell on a camper trailer in Putnam County as two people were riding out the storm, and a woman inside the trailer was killed, the sheriff's office said.

While Matthew didn't follow the worst-case-scenario path that meteorologists had feared, sparing the 4.4 million people in the Miami and Fort Lauderdale areas in South Florida from its havoc earlier, officials warned Florida, Georgia and the Carolinas weren't out of the woods yet.

"Unfortunately, the track just offshore in Florida gave people the impression that whew, we’ve dodged a bullet here, and that’s just not the case," Jamie Rhome, leader of the storm surge unit of the National Hurricane Center, warned Friday afternoon.

"Clearly you’re seeing the flooding in Jacksonville and northern Florida, and the closer track to the coast in Georgia and South Carolina is going to take these conditions northwards and impact those areas as well," he said.

Photos: Matthew Pounds the Coast

Meanwhile, the concern turned Friday from the path of the storm to its storm surge, which was forecast to be historic.

Storm surges of 7 to 11 feet were forecast near Daytona Beach, and were expected to move up into Georgia and South Carolina on Saturday morning. There were concerns about flash flooding and river flooding in coastal Georgia and South Carolina, NBC News meteorologist Bill Karins said.

The projected path of the storm:

Friday evening: Matthew barrels to northern coastal Florida

Friday evening through Saturday morning: The storm takes aim at the Georgia coast

Saturday afternoon and evening: South Carolina comes into the crosshairs

"This storm's a monster," Scott warned as the hurricane began pummeling his state. "I'm going to pray for everybody's safety."

Two million people up and down Florida had been ordered to evacuate, and some 3,500 members of the National Guard — half of the state's contingent — had been activated. Evacuations were also ordered in parts of Georgia and South Carolina.

"There is nothing safe about what's getting ready to happen," South Carolina Gov. Nikki Haley said of the storm surges, which could top 8 feet in her state.

In Swainsboro, Georgia, so many people packed into a shelter that Red Cross workers ran out of beds Thursday night.

"We were 30 cots short. We didn't have blankets for everybody," Jon Mayner, a Red Cross shelter manager, told NBC News.

Red Cross volunteers and firefighters put the word out on Facebook that the shelter was running low on supplies, and members of the community stepped up to help, he said.

"The community went down to Walmart and bought all their pillows and blankets and inflatable beds," he said. "A real testimony to what the U.S. is all about."

Still, elsewhere, others weren't following the evacuation orders. Obama on Friday warned those in the storm's path to listen to local authorities.

"Do what they say. Do not be a holdout, because we can always replace property, but we can't replace lives," he said.