A fire truck crosses a bridge ahead of the arrival of Hurricane Florence in Sunset Beach, North Carolina, U.S. September 12, 2018. REUTERS/Randall Hill

(Reuters) - Florence is now rated a Category 3 on the five-step Saffir-Simpson scale, but life-threatening storm surge and rainfall is still expected across portions of the Carolinas, the U.S. National Hurricane Center (NHC) said on Wednesday.

The hurricane was about 470 miles (755 km) east-southeast of Myrtle beach South Carolina, with maximum sustained winds of 125 miles per hour (205 km/h), the Miami, Florida-based weather forecaster said.

Although slow 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 late Thursday and Friday, the NHC added.