Helene made landfall in Florida's Big Bend region late Thursday night after it strengthened to a Category 4 hurricane earlier in the day.
Forecasters with the National Hurricane Center said the eye of the storm made landfall about 10 miles west-southwest of Perry, Florida, about 11:10 p.m. ET with maximum sustained winds of 140 mph.
The storm weakened to a Category 1 as it moved inland across Georgia but the threat of life-threatening storm surge, winds and heavy rain continued, the hurricane center said in a 2 a.m. Friday update.
Forecasters warned Helene could have a wind swath more than 400 miles wide and could bring "unsurvivable" storm surge.
Florida, Georgia, North Carolina and South Carolina have declared emergencies ahead of landfall.
Flooding is a concern in North Carolina, Georgia and South Carolina.
The system became a tropical storm Tuesday in the western Caribbean Sea and caused flooding in the Cayman Islands.