Breaking news update, published at 2:05 p.m. PT
Hurricane Matthew is now a Category 2 storm with maximum sustained winds of 110 mph, the National Hurricane Center said in its 5 p.m. update. Matthew is forecast to continue being a formidable hurricane as it approaches the coasts of Georgia and the Carolinas in the next few days.
Breaking news update, published at 1:56 p.m. PT
An 82-year-old man and a woman in her 60s have died during Hurricane Matthew, according to the Lucie County Fire Department and a spokeswoman at the Volusia County Community Information Center. This brings the toll of storm-related deaths in Florida to three.
Original story , published at 1:46 p.m. ET
Floridians along the Atlantic coast were coping Friday with rising water as Hurricane Matthew drenched the state with rain and strong winds pushed ocean water over beaches.
Meteorologists said storm surge had been measured at more than 4 feet in some areas.
The storm sparked flash-flood concerns. The National Weather Service issued a warning for parts of Nassau County, north of Jacksonville.
"This is a particularly dangerous situation. Seek higher ground now," the agency warned.
The Category 3 hurricane has left more than 1 million people without power as it skirts the state's east coast, with the most damaging blow possibly still to come.
Governors in North and South Carolina warned residents to get out in advance of the storm, which could drop as much as 15 inches of rain.
But it's not as if Matthew -- with winds of 115 mph at the center -- didn't cause any damage with its powerful winds.
Parts of St. Augustine flooded even as the hurricane was still approaching. A virtual river of water rushed past a bed and breakfast business in the city about 35 miles southeast of Jacksonville, according to video posted by reporter Russell Colburn of CNN affiliate WJAX.
Special concern surrounded Jacksonville's St. Johns River, which could be overwhelmed by water pushed into it by the storm.
"Just because the center of circulation is offshore doesn't mean you can't be the center of action (along the coast)," National Hurricane Center Director Rick Knabb said. "It's going to get a lot worse before it (has) a chance of getting better."
Here's what you need to know:
• As of 4 p.m. ET, Matthew's center was over the Atlantic, about 35 miles east of St. Augustine, the National Hurricane Center said. Hurricane-force winds extended outward up to 60 miles from that center. It was moving north at 12 mph.
• At least one Florida death has been linked to the storm -- a 50-year-old woman who died overnight after a heart attack in St. Lucie County, the county's emergency operations center said. The center considers it a storm-related death because firefighters had to stop responding to emergency calls because of high winds.
• Jacksonville could see storm surges of up to 9 feet Friday afternoon, forecasters said. Anything over 3 feet in the city is life-threatening, Mayor Lenny Curry said.
• "Very dangerous conditions, and it's going to get worse into the afternoon," Curry said.
• A total of 1.1 million customers statewide were without power.
• Forecasters predict storm surges in coastal Georgia and South Carolina also could be as high as 9 feet, and as many as 15 inches of rain could fall from central Florida to North Carolina.
• The National Weather Service warned that some places hit by Matthew could be uninhabitable for "weeks or months."
• The storm has killed at least 300 people in three Caribbean countries. The majority died in Haiti, said Civil Protection Service spokesman Joseph Edgard Celestin.
Though the storm hasn't made landfall, it left swaths of coastal Florida with downed trees and power lines.
Matthew kicked up debris and street flooding in Daytona Beach late Friday morning. Video recorded by journalist Robert Ray showed metallic, foil-like debris and other small objects rolling down one of the streets in the city.
Florida Govs. Rick Scott said officials are particularly concerned about low-lying areas in and around Jacksonville, where there is potential for significant flooding.
He said all major roads and interstate highways were open as of late morning, and no major road or traffic issues were reported. In some of the counties that the storm has passed, it appeared that evacuations urged by local officials worked, he said.
"While the storm is still on, don't go outside," Scott said.
More than 22,000 people were in shelters statewide, he said.
President Barack Obama urged people in coastal northeastern Florida and Georgia to heed the instructions of local officials as Hurricane Matthew approached.
"This is still a really dangerous hurricane," Obama said at the White House Friday. "We're not going to know for three, four, five days what the ultimate effects of this (storm) are."
Major southern Florida population centers such as Miami and West Palm Beach appeared to have avoided the worst of the storm, as the dangerous eyewall stayed about 100 miles off the coast.
Parts of the Miami area saw tropical storm force winds, but higher hurricane force winds were a couple hundred miles farther north. Winds knocked down power lines in Miami-Dade County, leaving tens of thousands without electricity. But only 1,000 customers were still in the dark Friday afternoon, Florida Power & Light said.
Officials in eastern Florida, Georgia and South Carolina urged people to evacuate coastal areas.
Airline passengers were urged to call and check on the status of their scheduled flights before leaving for the airport. Florida airports had canceled hundreds of flights, most of them in Miami, Fort Lauderdale and Orlando. Fort Lauderdale closed its airport, airlines suspended operations in Miami and Orlando's airport closed Thursday evening.
Georgia, South Carolina and North Carolina
As northeastern Florida braced for impact, coastal communities in Georgia, South Carolina and North Carolina also were on notice. The storm's center could be near or over the coasts of Georgia and South Carolina on Saturday, the hurricane center said.
• Glynn County officials wrote on Facebook that "Conditions have deteriorated to a point that persons remaining in (the area near Brunswick) are advised to shelter in place for the remainder of the storm."
• Maj. Tommy Tillman of the Chatham County Sheriff's Office said the road to Tybee Island is closed.
• In Savannah, Mayor Eddie DeLoach warned those who stay that they'd be on their own.
• Gov. Nathan Deal has ordered evacuations for all counties east of Interstate 95. Deal has activated 1,000 National Guard troops.
• Four counties and one city in South Carolina will be under nighttime curfews until further notice, said state Emergency Management Division spokesman Derrec Becker. Dorchester, Beaufort, Jasper and Williamsburg counties will be under curfew. Charleston's curfew starts at midnight. The curfews end each morning, at different times.
• Gov. Nikki Haley warned residents who didn't evacuate to go to a shelter. A major storm surge of 8 feet or more is approaching low-lying areas in the state, including Charleston.
• Although 310,000 people have evacuated the area, Haley says that's not enough. Officials in some areas are going door to door, urging people to leave. Police in Pawleys Island asked residents who decided to stay in spite of the evacuation orders to sign a waiver and list their next of kin, according to CNN affiliate WBTW.
• Gov. Pat McCrory said the forecast had change, to North Carolina's detriment. "What we feared is now happening in North Carolina. The (hurricane forecast) model has changed dramatically," he said. "The immediate concern is life-threatening rain and water (from storm surge)."
• Officials are concerned that eastern areas -- like Fayetteville, home to a large Army base -- that were recently flooded will see more rain from Matthew.