Updated at 11:57 a.m. E.T.

In Charleston, S.C., a major interstate is reversing direction for about 100 miles, sending every lane inland.

In the Outer Banks, N.C., where tourists and residents rely on a few bridges and ferries for access to the mainland, authorities are warning residents to get out immediately.

And in coastal Virginia, where the sun is shining and the sky is blue, the state's emergency management website crashed as hundreds of thousands of people tried to look up the mandatory evacuation maps.

Wide swaths of North Carolina, South Carolina and Virginia are preparing for the arrival of Hurricane Florence — currently a Category 4 storm with 130 mph maximum sustained winds that will also bring dangerous flooding and storm surges.

Florence is expected to hit those three states late Thursday or early Friday. Evacuation orders are going into effect for nearly the entire coasts of North and South Carolina on Tuesday, adding to orders that went out on Monday.

All told, more than a million people are under mandatory evacuation orders, according to FEMA. Many more are being urged to evacuate at-risk areas voluntarily.

Florence is expected to be a large, slow storm dropping massive quantities of rain on already-waterlogged land, with consequences extending well beyond the coast. Far inland — where evacuees will be taking refuge — flooding and power loss are still a serious risk.

FEMA recommends that anyone fleeing a hurricane take an emergency supply kit with them — including several days' worth of water, food and any necessary medical supplies, as well as flashlights, extra batteries, a first-aid kit and baby wipes for personal hygiene.

Evacuees should take their pets with them, along with pet food and supplies; they may not be allowed in all shelters, so be prepared to find pet-friendly hotels, kennels or family and friends to take them in. The Charlotte Observer has compiled some options in the Carolinas.

Evacuating a disaster area can be particularly difficult for the elderly, people with disabilities and people living in poverty.

Virginia Gov. Ralph Northam says local resources are available to help people who might have difficulty leaving their homes. When traveling is difficult, he says, it's even more important evacuate in advance. "We want to make sure that they have plenty of time to get to higher ground," hetold NPR on Tuesday.

Anti-price-gouging laws are now in effect in North Carolina and South Carolina; anyone witnessing exorbitant prices on gas, lodging or food along evacuation routes can complain to their attorney general's office.

On Monday night, the Trump administration granted a federal disaster declaration for North Carolina and South Carolina, designed to help speed aid to residents affected by Florence.

Virginia has asked for a similar declaration, Northamtells NPR.

In addition to evacuations, more than half of schools in 26 South Carolina counties are closed on Tuesday, with no reopening date set.

"Some schools in the inland counties will be used as shelters," McMaster said of that move. He added, "we want to keep the roads as clear as possible for the one million evacuees we are expecting."

North Carolina

At least six North Carolina counties are now under complete or partial mandatory evacuation orders: Brunswick, Currituck, Dare, Hyde, New Hanover and Onslow.

"Wherever you live in North Carolina, you need to get ready for this storm now and you need to evacuate if asked to," North Carolina Gov. Roy Cooper said.

The Outer Banks, a chain of barrier islands that are a popular tourist destination, are connected to the North Carolina mainland by just two bridges.

ABC's Gio Benitez, reporting from the Outer Banks, says authorities are urging people to leave well ahead of the storm, to avoid being stranded on those bridges.

"If they're on this road, on this highway when the storm hits, you're going to have a very dangerous storm surge," he reports. "It's going to be a very dangerous situation."

South Carolina

South Carolina Gov. Henry McMaster initially ordered a full coastal evacuation effective noon [Tuesday], issuing a a mandatory order for residents in hurricane evacuation zones along the state's entire coast.

On Tuesday morning, he adjusted that order based on new predictions from the National Hurricane Center. The southernmost parts of South Carolina — Beaufort, Colleton and Jasper counties — are no longer under a mandatory evacuation order. (Edisto Beach, however, is still being evacuated.)

South Carolina evacuation zones are available here, while evacuation routes can be viewed here.

To help facilitate the exodus of hundreds of thousands of people in South Carolina, lanes are being reversed on Interstate 26 to allow people to head only west – away from the coast and the massive storm. All four lanes of the interstate will be used for inland-bound traffic for some 100 miles, from Charleston to Columbia.

The lane reversal begins at noon ET, and before 9 a.m., troopers were already starting to clear out the lanes of east-bound traffic to prepare for the evacuation.

Virginia

In Virginia, Gov. Northam issued a mandatory evacuation order for coastal residents in "Zone A" — an area that includes parts of of Hampton Roads and the Eastern Shore. The order took effect at 8 a.m. ET Tuesday.

Residents of coastal Virginia can look up their evacuation zone here. The site crashed on Monday, overwhelmed by the number of visitors,The Virginian-Pilot reports. The department of emergency management had to put the site on a new set of servers to handle the demand.

NPR's Sarah McCammon, whose neighborhood in Virginia Beach is under an evacuation order, reports that as of Tuesday morning, the area was "pretty quiet."

"It really, so far, feels like any normal day," she says. "A lot of people are still around."

But people are clearly preparing for the storm, she said — local stores are already selling out of large bottles of water.

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