Hurricane Nicole hit Florida on Thursday with 70mph (110kph) winds but has been downgraded to a tropical storm after it slowed on making landfall.
States of emergency remain and evacuation orders are in place, with heavy rain and storm surges forecast.
Nicole has already lashed Grand Bahama Island as a huge category one hurricane, with the scale of the devastation not immediately clear.
Storms of this size so late in the year are extremely rare.
It could possibly even hit Ohio, Pennsylvania and New York later in the week.
The National Hurricane Center (NHC) upgraded Nicole on Wednesday evening from a tropical storm, then downgraded it again an hour after it made landfall and slowed.
A tropical storm warning is in place for the mid-section of Florida’s eastern coast which includes former president Donald Trump’s Mar-a-Lago club in West Palm Beach, with the NHC warning of “strong winds, dangerous storm surge and waves, and heavy rains”.
Forty-five of the state’s 67 counties are under a state of emergency and four counties are under mandatory evacuation orders.
More than 100,000 customers have been left without power by the storm.
The arrival of Nicole is also expected to further disrupt a long-delayed Nasa rocket launch, which aims to bring Americans one-step closer to returning to the Moon.
The Artemis 1 mission had already been pushed back to 19 November but there are fears that flying debris caused by the storm could damage the exposed rocket.
Nicole’s late arrival follows a relatively quiet storm season – for the first time since 1997 not a single hurricane or tropical storm formed in the Atlantic basin this August.