Hurricane Matthew has strengthened to a catastrophic Category 4 storm as it barrels toward the heavily populated coast of Florida.

The National Hurricane Center in Miami said the storm’s maximum sustained winds had strengthened to 140 mph as of late Thursday morning and were expected to maintain their strength as the storm approaches the Florida coast.

Hurricane conditions were also still affecting the Bahamas. The storm was expected to start affecting Florida by early afternoon Thursday.

Two counties along South Carolina’s northern coast are being evacuated ahead of Hurricane Matthew.

Gov. Nikki Haley told reporters evacuation orders go into effect at noon Thursday for parts of Horry and Georgetown counties. Haley warned anyone in an evacuation zone not to take the orders lightly. She says surge from the storm could be as high as 8 feet and affect not only the coast but also areas farther inland.

So far, Haley says 175,000 people have evacuated from the coast. On Wednesday, the state reversed the eastbound lanes of Interstate 26 from Charleston to Columbia, allowing more motorists to move inland at once.

Forecasters say they expect Matthew to strengthen to a Category 4 hurricane before making landfall in Florida, turning north and passing just off the South Carolina coast late Friday or early Saturday.

North Carolina Gov. Pat McCrory says the latest predictions show that his state will avoid a direct hit from Hurricane Matthew.

But emergency workers are continuing to prepare for high winds, rain and storm surge.

McCrory says North Carolina cities like Jacksonville and Morehead City could still see wind gusts of up to 60 mph beginning Saturday. Widespread power outages are possible. There could be a foot of rain in some areas.

The National Hurricane Center in Miami says the hurricane is strengthening and called it dangerous and life-threatening. About 1.5 million people in Florida have been ordered to evacuate.

The head of the Bahamas National Emergency Management Authority says the capital Nassau is now receiving the full brunt of Hurricane Matthew.

Capt. Stephen Russell says there are many downed trees and power lines but no immediate reports of significant flooding or casualties as of early Thursday. Russell says Nassau should feel the full effects of Matthew for much of the day.

“We are experiencing the brunt of the hurricane force winds now so we just have to wait and see how we fare over the next five of six hours,” he told The Associated Press.

Nassau is on the most populous island of New Providence in the central Bahamas. The streets were deserted as palm fronds flew through the air under heavy rain. Those in Nassau without generators are without power because authorities shut down the power when winds reach 40 mph to protect the grid. The major tourist hotels are on generator power.

The storm is now clear of the lightly populated islands of the southern Bahamas and Russell says there are no reports of any significant damage or casualties on those islands.