Powerful Hurricane Florence was tracking towards the US East Coast Tuesday, prompting authorities to order upwards of one million people to evacuate the path of the extremely dangerous storm forecasters said could soon intensify.

Residents scrambled to flee en masse as the menacing Category 4 storm packing winds of 220 kilometers per hour bore down on the East Coast of the United States.

"This is one of the worst storms to hit the East Coast in many years," President Donald Trump warned on Twitter. "Please be prepared, be careful and be SAFE!"

South Carolina Governor Henry McMaster ordered as many as one million residents of the state's eastern coast to leave their homes ahead of the storm's possible arrival on Thursday. Schools in 26 of the state's 46 counties were to close from Tuesday.

The governor of neighboring North Carolina ordered an evacuation of the Outer Banks, barrier islands that are a popular tourist destination, and parts of coastal Dare County, while a state of emergency was declared in Virginia.

"This is a very dangerous hurricane," McMaster said, adding that the evacuation order for coastal counties was "mandatory, not voluntary."

"We do not want to risk one South Carolina life in this hurricane," the governor told reporters. "We're liable to have a whole lot of flooding." </s> Hurricane Florence, a powerful Category 4 storm, threatens to hit North and South Carolina, as well as a large part of the southeastern US coast, though the storm is expected to slightly weaken by Thursday, the National Hurricane Center (NHC) said Wednesday.

"While some weakening is expected to begin by late Thursday, Florence is still forecast to be an extremely dangerous major hurricane when it nears the U.S. coast on Friday," the Miami-based NHC said in its 15:00 GMT public advisory. </s> More than 1.5 million people were ordered to evacuate their homes along the U.S. Atlantic coast as Hurricane Florence, a Category 4 storm and the most powerful to menace the Carolinas in nearly three decades, barreled in on Tuesday.

Florence, packing winds of 140 miles per hour (220 kph), was expected to grow even stronger before making landfall on Thursday, mostly likely in southeastern North Carolina near the South Carolina border, the National Hurricane Center in Miami said.

"We are in the bull's eye," North Carolina Governor Roy Cooper told reporters on Monday.

Florence was expected to turn into "an extremely dangerous major hurricane" during Thursday night, the hurricane center said in a bulletin.

Virginia Governor Ralph Northam issued an evacuation order for about 245,000 residents in flood-prone coastal areas beginning at 8 a.m. local time and South Carolina Governor Henry McMaster ordered more than 1 million residents along his state's coastline to leave starting at noon on Tuesday.

At least 250,000 more people were due to be evacuated from the northern Outer Banks in North Carolina on Tuesday after more than 50,000 people were ordered on Monday to leave Hatteras and Ocracoke, the southernmost of the state's barrier islands.

North Carolina, South Carolina, Virginia and Maryland governors have declared states of emergency.

Authorities warned of life-threatening coastal storm surges and the potential for Florence to unleash prolonged torrential rains and widespread flooding, especially if it lingers inland for several days.

NHC Director Ken Graham warned of "staggering" amounts of rainfall that may extend hundreds of miles inland and cause flash flooding across the mid-Atlantic region.

Forecasts expect 10 to 15 inches (25-38 cm) of rain in the hardest-hit areas, possibly more if the storm stalls over land, as expected, Graham said.

Mindful of devastation wrought by a string of deadly U.S. hurricanes last year, residents in the Carolinas began the rituals of disaster preparation - boarding up windows and stocking up on groceries, water and gasoline.

Classified as a Category 4 on the five-step Saffir-Simpson scale of hurricane strength, Florence was the most severe storm to threaten the U.S. mainland this year and the first of its magnitude to target the Carolinas since 1989, when Hurricane Hugo barreled over Charleston, South Carolina.

In Holden Beach, North Carolina, in the storm's path, longtime residents were busy securing their homes and possessions.

"It's scary to all of us. We know we can't play around with this," said Jennifer Oosterwyk, who owns the Sugar Britches boutique on Holden Beach and lives in nearby Wilmington. </s> Hurricane Florence intensified Monday, becoming a Category 4 storm, according to the National Hurricane Center (NHC).

The storm may affect millions this week in the southeastern U.S., including North Carolina, South Carolina and Virginia.

Here’s what should you know about the powerful storm’s path.

Where is the hurricane now?

Florence is approximately 410 miles south of Bermuda and 975 miles east-southeast of Cape Fear, North Carolina, as of 5 a.m. ET, according to the NHC.

The center says the storm is moving west-northwest at 15 miles per hour, and has maximum sustained winds of about 140 miles per hour.

"On the forecast track, the center of Florence will move over the southwestern Atlantic Ocean between Bermuda and the Bahamas Tuesday and Wednesday, and approach the coast of South Carolina or North Carolina on Thursday," the center said.

The NHC also says the storm could become more powerful.

"Florence is a category 4 hurricane on the Saffir-Simpson Hurricane Wind Scale," it noted. "Further strengthening is anticipated, and Florence is expected to be an extremely dangerous major hurricane through Thursday."

WHAT IS THE SAFFIR-SIMPSON HURRICANE WIND SCALE?

What else should I know?

The governors of North and South Carolina and Virginia have all declared states of emergency ahead of the approaching storm.

HURRICANE FLORENCE STRENGTHENS IN ATLANTIC: TIPS TO PREPARE FOR THE STORM

“Pretend, assume, presume that a major hurricane is going to hit right smack dab in the middle of South Carolina and is going to go way inshore,” South Carolina Gov. Henry McMaster advised.

The state’s emergency management agency said it is “preparing for the possibility of a large-scale disaster.”

President Trump declared a state of emergency in North Carolina ahead of the storm.

"Please be prepared, be careful and be SAFE!" he tweeted Monday evening.

If you're getting ready for Florence, you can read about steps to prepare for the storm here.

Fox News' Kaitlyn Schallhorn and The Associated Press contributed to this report. </s> A satellite image taken the morning of September 10, 2018, shows Hurricane Florence off the US East Coast in the Atantic Ocean.

A coastal North Carolina county on Monday issued a mandatory evacuation order for its entire population as a Hurricane Florence strengthened to a Category 3 storm and continued its slow but angry dance toward the U.S. East Coast.

The National Hurricane Center said Florence is expected to slam into the coast around North and South Carolina as a Category 3 or 4 hurricane on Thursday or Friday. The storm's winds had increased to 115 mph on Monday.

North Carolina Gov. Roy Cooper said he had asked President Trump for a federal disaster declaration ahead of the storm.

"We here in North Carolina are bracing for a hart hit," Cooper said Monday. "We are taking Hurricane Florence seriously."

Dare County officials ordered everyone to leave Hatteras Island on Monday. Residents and visitors in popular tourist spots such as Duck and Corolla faced a Tuesday deadline.

"Everyone in Dare County is encouraged to evacuate as soon as possible regardless of the established time frames," the county announced.

Dare County has a year-round population of more than 30,000 people, but the population balloons during tourist seasons. It was not immediately clear how many people.

The hurricane center said the storm was expected to continue growing in strength through the day. The center of Florence was forecast to sweep between Bermuda and the Bahamas on Tuesday and Wednesday before making its assault on the U.S. coast.

"Florence is forecast to become a major hurricane this morning, and is expected to remain an extremely dangerous major hurricane through Thursday," the hurricane center warned.

More: Despite 2017 hurricane season, US lacks 'culture of preparedness'

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The hurricane center warned that the swells are likely to cause "life-threatening" surf and current conditions. Even before the evacuation order, Dare County emergency officials warned that rough seas and strong rip currents are already creating dangerous conditions.

"Red, no swimming flags are flying and everyone must stay out of the water," Dare County Emergency Management Director Drew Pearson said.

Satellite imagery indicated that the maximum sustained winds have increased to near 105 mph with higher gusts. A "major" hurricane is one with sustained winds of more than 110 mph.

Any Category 3, 4, or 5 hurricane is classified as a major hurricane.

AccuWeather meteorologist Brett Rossi said the ground in North and South Carolina and Virginia is already saturated from recent rains. Rivers are high, and the storm will be moving slowly when it arrives, exacerbating the situation, Rossi told USA TODAY.

"This is very scary rain event potentially setting up this week," Rossi said. "Florence could dump a foot of rain in places that cannot handle it, making for a very scary flooding situation in some areas."

Some portions of the Carolinas could see as much as 20 inches of rain from Florence, the National Weather Service said, which would lead to river flooding that "could last for days or weeks" after the storm. The Weather Channel warned of a "disastrous" level of flooding for parts of the area.

The hurricane center's breakdown of storm strength says Category 3 storms can bring "devastating" destruction. Homes can be damaged, trees uprooted and electricity and water can be knocked out for days or weeks, the center warns.

The Navy said all ships in Virginia's coastal Hampton Roads area were preparing to leave port for open seas Monday. Admiral Christopher Grady said ships can better weather "storms of this magnitude when they are underway."

South Carolina emergency management officials said they were "preparing for the possibility of a large-scale disaster."

Virginia, North and South Carolina have declared states of emergency ahead of the storm.

"The storm is strong and getting stronger," Gov. Roy Cooper said. "The best safety plan is preparation and common sense."

Florence is now one of three hurricanes spinning in the Atlantic Ocean, along with Helene and Isaac. While Helene is forecast to slide out to sea away from land, Isaac is a very real threat the the Caribbean later this week, the hurricane center said.

In addition, in the Pacific, what's now Hurricane Olivia is forecast to approach Hawaii as a tropical storm on Tuesday. </s> Hurricane Florence has hit the US coast leaving streets inundated with ocean water and tens of thousands of homes without power.

The centre of the hurricane made landfall near Wrightsville, North Carolina, bringing with it life-threatening storm surges and 145km/h (90m/h) winds.

The National Hurricane Centre warned there would be “catastrophic” fresh water flooding over a wide area of the Carolinas.

More than 60 people had to be evacuated from a motel at risk of collapse in Jacksonville. Parts of buildings ripped apart by the storm flew through the air.

Authorities in the North Carolina city of New Bern said there are about 150 people waiting to be rescued from rising flood waters.

The US National Hurricane Centre said that a gauge in Emerald Isle, North Carolina, recently reported 1.92m (6.3ft) of inundation. Emerald Isle is about 135km (84 miles) north of Wilmington.

Screaming winds bent trees and led to near-horizontal rain as Florence’s leading edge whipped the Carolina coast to begin an onslaught that could last for days, leaving a wide area underwater from both heavy downpours and rising seas.

The storm’s intensity diminished as it neared land, with winds dropping to around 145km/h (90m/h) .

Governor Roy Cooper has warned of an impending disaster. He said: “The worst of the storm is not yet here but these are early warnings of the days to come.

“Surviving this storm will be a test of endurance, teamwork, common sense and patience.”

Mr Cooper requested additional federal disaster assistance in anticipation of what his office called “historic major damage” across the state.

More than 80,000 people were already without power as the storm began buffeting the coast, and more than 12,000 were in shelters. Another 400 people were in shelters in Virginia, where forecasts are less dire.

Prisoners were affected, too. North Carolina corrections officials said more than 3,000 people were relocated from adult prisons and juvenile centres in the path of Florence, and more than 300 county prisoners were transferred to state facilities.

Officials said some 1.7 million people in the Carolinas and Virginia were warned to evacuate, but it is unclear how many did.

The homes of about 10 million are under watches or warnings for the hurricane or tropical storm conditions.

Forecasters said conditions will deteriorate as the storm pushes ashore near the North Carolina-South Carolina line and makes its way slowly inland.

Its surge could cover all but a sliver of the Carolina coast under as much as 11ft of ocean water, and days of downpours could unload more than 3ft of rain, touching off severe flooding.

Although it was once a Category 4 hurricane with winds of 225km/h (140m/h), the hurricane was downgraded to a Category 1 on Thursday night.

Forecasters said that given the storm’s size and sluggish track, it could cause enormous damage similar to what the Houston area saw during Hurricane Harvey just over a year ago, with floodwaters swamping homes and businesses. </s> Hurricane Florence was upgraded to a Category 4 storm by the National Hurricane Center on Monday afternoon, and it is bearing down on the east coast of the United States. Updated models showed the eye of the storm to be East-Southeast of Cape Fear, North Carolina, and moving toward the South Carolina/North Carolina boarder at 13 miles per hour.

Recent models show the storm making landfall late Thursday night or early Friday morning anywhere from Charleston, South Carolina, to Norfolk, Virginia. When it does, meteorologists are predicting Florence to weaken and sit over the east coast of the United States for a significant period of time, which could create major flooding.

The severity of the storm and the time in which it is expected to make landfall will put the status of several FBS football games in doubt for Week 3 of the season.

It has already forced Coastal Carolina to move its game against Campbell up three days from Saturday to Wednesday. That game will kick at 2 p.m. ET at Barker-Lane Stadium in Buies Creek, North Carolina, with free admission for all.

Here’s a list of more games that could be affected:

Mandatory evacuation is already in place for Hatteras Island, North Carolina. A state of emergency has already been declared for South Carolina, North Carolina and Virginia. Because of the danger that already exists, and potentially more evacuations to come, Duke’s road trip to Baylor could be another game impacted by the approaching storm. </s> Emergency officials on Wednesday urged millions of residents along the southeastern U.S. coast to finish preparations ahead of Hurricane Florence, which is expected to unleash damaging winds and life-threatening amounts of rain when it makes landfall this week.

Florence was at last report a Category 3 storm with maximum sustained winds of 195 kilometers (121 miles) per hour. Although it weakened slightly Wednesday afternoon, forecasters do not expect Florence’s strength to change much before it comes ashore near the North Carolina-South Carolina border.

The massive system was about 700 kilometers (435 miles) southeast of Wilmington, North Carolina. The National Hurricane Center said Florence was “forecast to be an extremely dangerous major hurricane when it nears the U.S. coast late Thursday and Friday.”

“This is not going to be a glancing blow,” the Federal Emergency Management Agency’s Jeff Byard said in Washington.

The governors of the Carolinas, Virginia, Maryland and Georgia all declared states of emergency.

Byard again urged residents in danger zones to heed warnings to either evacuate or hunker down. “There will be disruptions in our services,” he said. “The power will go off. Infrastructure will be damaged. Homes will be damaged or destroyed. So, again, the time to act is now.”

There was particular concern about the storm lingering once it nears the coast and moves onshore, allowing it to dump torrential amounts of rain in parts of North Carolina, South Carolina and Virginia. That happened last year when Hurricane Harvey dumped more than 150 centimeters (60 inches) of rain on the Houston, Texas, area.

Forecasters at the hurrican center warned that as much as 101 centimeters (40 inches) of rain could fall on some parts of North Carolina, with a storm surge of up to 4 meters (13 feet).

Along with the high winds and storm surge, forecasters are very concerned that Florence could be a slow-moving storm. It could linger along the Atlantic Coast, dumping massive amounts of rain before drifting inland and bringing its heavy rainfall across the South and into the Mid-Atlantic states by early next week.

President Donald Trump said his administration was “as ready as anybody has ever been” to respond to the storm.

“We’ll handle it. We’re ready. We’re able,” Trump said Wednesday outside the White House. “We’re fully prepared. Food, medical, everything you can imagine, we are ready.”

The president signed federal emergency declarations for the Carolinas and Virginia, a move that freed up federal money and resources. He also urged residents who live in the path of the storm to “get out of its way. Don’t play games with it. It’s a big one.”

More than 1 million people along the coasts of North and South Carolina and southern Virginia have fled. They have faced gas shortages at some stations, while those who have chosen to stay put are clearing store shelves of emergency supplies.

Experts said this could be the strongest storm to hit the Carolina coast in more than 60 years.

The most powerful and only Category 4 hurricane in recorded history to hit the North Carolina coast was Hurricane Hazel in October 1954. Nineteen people in North Carolina were killed, and 15,000 homes were destroyed. </s> • The outer bands of Hurricane Florence have started to hit the coast of the Carolinas as it was downgraded to a Category 1 storm late Thursday night, with sustained winds topping 90 mph.
• The National Hurricane Center warned of "life-threatening storm surge and rainfall" in the Carolinas and mid-Atlantic states.
• Hurricane and storm surge warnings are in effect from the South Santee River in South Carolina to Duck, North Carolina.
• Over 5 million people are under hurricane warnings and watches as of Thursday morning.

The outer bands of Hurricane Florence have started to hit the coast of the Carolinas as it was downgraded to a Category 1 storm late Thursday night, with sustained winds topping 90 mph.

Hurricane Florence's center is expected to make landfall somewhere near the border between North and South Carolina on Friday, according to the National Hurricane Center (NHC), bringing life-threatening storm surge and rainfall.

But the storm's intensity is already being felt — weather stations along the North Carolina coast have registered sustained wind speeds of up to 53 mph, with gusts up to 74 mph.

"If you are in the path of Florence, please stay safe and take shelter today," FEMA said on Twitter Thursday morning. "Communicate with family and friends. Let them know where you are and how you’ll stay in touch."

The NHC has issued hurricane and storm surge warnings for the coastal areas between the South Santee River in South Carolina and Duck, North Carolina as well as Albemarle and Pamlico Sounds. A storm surge watch previously announced for areas north of Duck, North Carolina were canceled.

Powerful waves and walls of water are expected to rush inland when the storm arrives, bringing catastrophic flooding. North Carolina's barrier islands, from Cape Fear to Cape Lookout could see the biggest storm surge: between 9 and 11 feet.

Parts of North Carolina's coast, including Hatteras and the Outer Banks, are already experiencing waves of around 30 feet, according to National Oceanic and Atmospheric Administration buoys.

Much of the rest of the Carolina coastline, from the Virginia border down to Edisto Beach, South Carolina is under hurricane and storm surge watch. Hurricane-force winds extend up to 80 miles from Florence's center and tropical-storm-force winds extend outward up to 195 miles.

The NHC issued an additional tropical storm warning south of Santee River to Edisto Beach on Thursday.

"This is a very serious storm. The power could go out for many weeks," Brock Long, the administrator of the Federal Emergency Management Agency, said Thursday morning.

Florence was expected to slow down considerably late Thursday going into Friday, according to the NHC, meaning it will likely sit over the Carolinas late into the weekend, pounding the area near the shore with rain.

Read More: Where Hurricane Florence's eye is due to make landfall

Around 5.25 million people live in areas under hurricane warnings or watches, and 4.9 million live in places covered by tropical storm warnings or watches, the National Weather Service said, per The Associated Press

"Storm surge is why many of you have been placed under evacuation, and we are asking citizens to please heed the warning. Your time is running out," Long said.

Florence was hovering about 50 miles south of Morehead City, North Carolina, late Thursday night and 60 miles southeast of Wilmington, North Carolina. The storm was moving northwest at about 6 mph.

Five states have declared states of emergency ahead of the storm: Georgia, South Carolina, North Carolina, Virginia, and Maryland, along with Washington, DC.

Evacuation orders are in place in one of South Carolina's four coastal counties. Virginia's governor, Ralph Northam, issued a mandatory evacuation order for residents of the state's low-lying coastal areas as well. In North Carolina, evacuations have been ordered in Dare County, which includes the Outer Banks, as well as other coastal counties, according to The Observer.

In a press conference on Wednesday, North Carolina's governor, Roy Cooper, warned residents: "Disaster is at the doorstep. If you're on the coast there is still time to get out safely."

The storm could leave thousands of buildings flooded. Duke Energy, the Carolinas' major power supplier, said up to 3 million customers could lose power, perhaps for weeks, according to The New York Times.

"This may be a marathon, not a sprint," Cooper added.

Read More: The 14 most important things you should do to prepare for a hurricane

Florence is currently a Category 1 hurricane, meaning it has maximum wind speeds between 74 and 95 mph.

Predicting hurricane paths is a difficult science, and there are still uncertainties about this storm's track. But if predictions hold, Florence's center could make landfall near Wilmington, North Carolina on Friday morning.

"A life-threatening storm surge is now highly likely along portions of the coastlines of South Carolina and North Carolina, and a storm surge warning is in effect for a portion of this area," the NHC said Thursday.

The chart below shows the probability that an area that will see winds of at least 39 mph. The area in purple corresponds to a 90% or higher probability of experiencing those gusts.

Hurricane Florence is predicted to slow over the Carolinas and Virginia, where rainfall totals could reach 40 inches.

Heavy rain, up to 10 inches, may extend as far inland as Charlotte, North Carolina's largest city, and Raleigh, its capital. The NHC also said the storm's effects — including rain, high winds, rip currents, and tidal surges — would most likely be felt outside the "cone of probability" and could extend hundreds of miles from the storm's center.

Sluggish or stalled hurricanes — like Hurricane Harvey, which flooded swaths of Houston, Texas, and the Gulf Coast last year — can become even more dangerous as they stick around, pouring rain.

These types of slow-moving hurricanes are becoming more frequent. Recent research from the National Oceanic and Atmospheric Administration found that storms had slowed by an average of 10% over land between 1949 and 2016.

Read more: Why the deluge from Hurricane Florence could could be so intense

Other storms are churning as well

There are three other named storms in the Atlantic right now. Tropical Storm Isaac is about 220 miles southeast of Santo Domingo, the capital of the Dominican Republic, with sustained wind speeds of about 40 mph. The NHC has issued a tropical storm warning for the islands of Martinique, Dominica, and Guadeloupe.

Tropical Storm Helene has wind speeds of 65 mph, and will likely approach the Azores, an autonomous region of Portugal, late Saturday or Sunday. It's not close enough to land for any watches or warnings to be in effect now, though.

Meanwhile, in the Pacific Ocean, Super Typhoon Mangkhut is expected to make landfall in the Philippines on Saturday. It has sustained wind speeds of to 150 mph, and could be bigger and stronger than Florence when it hits land. The storm is then expected to move toward southern China, Vietnam, and Laos.

Tropical Storm Olivia has passed Hawaii, and tropical storm warnings have been lifted.
• Hurricane Florence could dump up to 40 inches of rain on parts of the Carolinas — here's why the deluge may be so intense
• 'Watch out, America!': Astronauts in space photographed Hurricane Florence, and they say the view is 'chilling'
• Watch storm conditions on these livestreams of North and South Carolina beaches in Hurricane Florence's path
• Hurricane Florence is a Category 2 storm — here's what those labels really mean
• The 14 most important things you should do to prepare for a hurricane
Hurricane Florence regains strength to a category 4 major hurricane and is expected to threaten the East Coast of the United States near the Carolinas in the coming days, with the potential for a category 4 or 5 landfall with very large rainfall totals. Preparations are underway for evacuation of around 1 million coastal inhabitants of South Carolina.