South Carolina has ordered the mandatory evacuation of its entire coast, and evacuations were also ordered for several North Carolina towns, as Category 4 Hurricane Florence continues her aggressive pursuit towards the states.

The governor of South Carolina, Henry McMaster, ordered the mandatory evacuation of the state's entire 187-mile coastline at noon on Tuesday.

"This is a real hurricane we have coming," he said. "We don't want to risk one South Carolina life."

The evacuation order extends to eight counties along the state's coast, with McMaster estimating that around one million people - residents and visitors - will be affected by the order.

North Carolina's governor declared a state of emergency on Sunday, one day after South Carolina. So far, mandatory evacuation orders have been issued for residents and visitors in some coastal areas of the state, while other counties only issued them for those in low lying and "flood prone" areas.

The governors of Maryland and Virginia have also declared a state of emergency.

Hurricane Florence was upgraded to a Category 4 earlier on Monday, with President Donald Trump taking to Twitter to encourage those in its path to "take all necessary precautions."

Central North Carolina's coastal counties are bracing for Florence to hit the area on Thursday, bringing potential floods and a threat of tornados, according to Dare County officials.

US Airmen from the National Guard and 169th Fighter Wing prepare for rescue efforts on September 10, 2018.Reuters

The hurricane is expected to "bring life-threatening storm surge, tropical storm force winds, heavy rains and the potential for tornadoes" to Dare and other coastal counties, said the National Weather Service, which has predicted that nine to 12.5 inches of rain will fall in some coastal counties between Thursday and Monday.