Hurricane Hermine has become the first to hit Florida in 11 years.
Hermine has made landfall in northern Florida early on September 2 as a Category one hurricane, bringing with it a heavy storm surge.
Florida Governor Rick Scott declared a state of emergency for 51 counties as residents were braced for the dangerous storm.
Wind gusts reached 80mph on September 1, the National Hurricane Center (NHC) said.
City officials in the state capital Tallahassee, which is in the path of the storm, said at least 70,000 homes were now without power.
Tallahassee weather officials warned of the risk of flash floods and urged people there to move to higher ground, but winds have now started to reduce as the storm moves inland.
While the area is prone to storms and storm surges, it has not seen a hurricane in close to 4,000 days.
The last hurricane to strike Florida was Wilma in October 2005, which made landfall in the same year as Katrina and caused five deaths and an estimated $23 billion of damage.
Gov. Rick Scott said: “This is life threatening. We have not had a hurricane in years.”
He added that 8,000 members of the Florida National Guard were prepared to be deployed in the wake of the storm.
Rick Scott ordered evacuations in five counties in Florida’s north-west and called for voluntary evacuations in three other coastal counties.
St Petersburg was littered with downed palm fronds and tree branches, and low-lying streets were flooded.
According to weather officials, Hurricane Hermine will also hit Georgia and the Carolinas, and could bring heavy rains along the East Coast in the coming days.
Georgia Gov. Nathan Deal has declared a state of emergency for 56 counties.