"This is a very unsafe hurricane", Mr McMaster said, adding that the evacuation order for coastal counties was "mandatory, not voluntary".
In addition to inundating the coast with wind-driven storm surges of seawater as high as 9 feet (2.7 meters) along the Carolina coast, Florence could dump 20 to 30 inches (51-76 cm) of rain, with up to 40 inches (1 metre) in parts of North Carolina, the NHC said.
A long stretch of the U.S. Eastern Seaboard remained vulnerable to hurricane and tropical storm conditions, from Georgia north through the Carolinas into Virginia.
Nighttime winds have gone from 140mph (225kph) to 115mph (185kph), and further weakening is expected as Florence approaches the coast.
The "threat of freshwater flooding will increase over the next several days" in the impacted areas.
Florence was located about 325 miles (520 km) east-southeast of Myrtle beach, South Carolina, with maximum sustained winds of 110 miles per hour (175 km per hour), the Miami, Florida-based weather forecaster said.
Causey, a former insurance agent who was elected as commissioner in 2016, said the NCDOI has been in touch with agent associations, carriers, FEMA, other states nearby that can provide resources, and the North Carolina Coastal Insurance Property Pool (the Beach Plan), which insures seven out of 10 homes along the state's coast.
Dangerous Hurricane Florence edged closer Thursday to delivering a powerful blow to the east coast of the United States, with forecasters warning of life-threatening rainfall and flooding even as it weakened to a Category 2 storm.
Florence will then recurve across the western Carolinas and the central Appalachian Mountains early next week.
The storm is expected to strengthen on Thursday before making landfall late Thursday night or early Friday.
The slow-moving storm is expected to bring hurricane winds to America's east coast within 24 hours.
Image SC National Guard
And if Florence weren't enough, other storms out there are threatening people.
North Carolina Governor Roy Cooper told a news conference that the "historic" hurricane would unleash rains and floods that would inundate nearly the entire state in several feet of water.
"There is going to be a lot of rain".
Steering currents - around clear-weather high-pressure systems and stormy low-pressure systems - redirect hurricanes, with the clear-weather systems acting as walls that storms have to go around.
One of the main dangers from hurricane Florence is the rainfall, added the spokesperson. As of Saturday, about 676,000 homes and businesses were without power in North Carolina, along with 119,000 in SC. "Japan was also exposed to very intense rainfall, leading to flooding and landslides, with casualties". Water could reach up to 13 feet above ground in parts of North Carolina and rainfall totals could get up to 40 inches in isolated areas there, and up 20 inches are possible in parts of SC.
People in areas vulnerable to the risky hurricane, particularly those in coastal regions, have fled ahead of the storm. Airlines canceled almost 1,000 flights and counting.
Hurricane Florence's path could affect the homes of more than 5 million people, and more than 1 million of them have been ordered to evacuate.
Eventually, Florence will veer north into the Appalachian Mountains, bringing soaking rains to Virginia and western North Carolina, before sputtering out late next week near DE and Maryland, the FWS reported.
About 1.7 million people have already been told to leave their homes in the latter three states, but some who thought they were safely out of the path of the storm are now desperately working to board up their homes and businesses before its arrival.
Tropical storm-force winds extended 195 miles from Florence's centre, and hurricane-force winds reached out 70 miles. The hurricane centre also adjusted its projected track, but kept it north of what most computer models were showing, to provide some continuity with past forecasts.
A Hurricane Watch is in effect for...