Pensacola, Florida - Isaias weakened from a hurricane to a post-tropical cyclone early Saturday after it made landfall in northwestern Florida, where it lashed the Gulf Coast with heavy rain and strong winds, the National Hurricane Center (NHC) said.
"Isaias has very rapidly weakened over Alabama and has transitioned into a post-tropical cyclone," the NHC said in an update.
The cyclone should move northward and north-northeastward at the weekend and gradually weaken as it moves across the Tennessee and Ohio valleys, the NHC added.
Isaias earlier made landfall near Destin, Florida, with authorities warning of "life-threatening storm surge impacting Gulf Coast as dangerous hurricane conditions and flash flooding spread inland."
Coastal communities saw mandatory evacuations and shuttered businesses as Isaias became the first hurricane of an Atlantic season that kicked off in June, held in check by a historic El Nino phenomenon that typically spurs more major storms in the Pacific.
In Pensacola, about 50 miles (80 kilometers) west of Destin in Florida, an AFP reporter witnessed howling winds rip the roofs from some homes and businesses, snapping tree branches as the power went out.
"Things are flying really fast, and I've never seen wind this fast before, so it's intense, it's scary," Jonathan Ramos, a 40-year-old government employee, told AFP at his hotel in Pensacola, where the power went out.
"I don't recommend people coming down here for fun to do this."
More than 300,000 customers in Florida and 200,000 in Alabama were without power on Friday night, according to poweroutage.us.
Earlier Friday, caravans of repair trucks rolled through the cities of Pensacola and Navarre to staging areas in preparation for power outages, AFP reporters on the scene said. Water service to buildings was suspended.