More than 664,000 customers in Florida and Alabama have been left without power as Isaias downs trees, power lines.

Hurricane Isaias has crashed into the United States Gulf Coast before losing speed and turning into a post-tropical storm as it moved over southern Alabama, threatening flash flooding and strong winds farther inland.

The US National Hurricane Center (NHC) said on Saturday that Isaias is about 89km (55 miles) south-southwest of Montgomery, with maximum ⁠sustained winds of 100 kilometres per hour (65 ⁠miles per hour).

When it made landfall near Destin, Florida, as the first hurricane of the Atlantic season, Isaias had maximum sustained winds of 169km/h (105mph), the agency said.

Roads in Destin were flooded, while in nearby Pensacola, police warned residents to stay off the streets because of debris across roadways.

While the extent of the damage was not immediately known, many area residents posted pictures online of downed trees and power lines, and one social media video showed a roof being ripped off an inn in Pensacola.

Some Panhandle counties temporarily suspended their emergency response on Friday night because of dangerous conditions.

Parts of southern Alabama were also flooded, with officials in Mobile reporting downed trees and power lines.

Roads in Houston County, which is in the southeastern corner of the state, were closed because of similar conditions.

More than 664,000 customers in Florida and Alabama were without power early Saturday, according to poweroutage.com.

One of the biggest concerns is a storm surge that could reach 0.91-1.52 metres (3-5ft) from Dauphin Island, Alabama, to Florida’s Aucilla River, according to the hurricane centre.

The storm grounded most Friday flights at several airports, including all flights in and out of Destin-Fort Walton Beach Airport.

‘Under control’

Asked about hurricane preparations, President Donald Trump ⁠told reporters outside the White House, “We’re watching it very ⁠closely, the hurricane,” adding that it was “under control”.

Florida’s National Guard deployed about 5,000 soldiers and airmen to help with the response, with search-and-rescue teams ready to respond, while some prisons evacuated inmates.

“Emergency declarations have ‌been approved in Florida and Alabama to ensure federal resources are available to respond to Isaias,” Homeland Security Secretary Markwayne Mullin said on X, as residents ‌were urged to take shelter and watch out for hurricane conditions.

Another tropical storm, Rachel, was also expected to bring strong winds and rain to northern Mexico and Southern California over the weekend.

And Simon has strengthened into a powerful Category 4 hurricane as it barrelled towards Mexico’s coast early on Saturday.

The NHC said Simon’s maximum sustained winds increased to 225km/h (140mph). A storm of that strength or greater is considered a major hurricane.

Simon is expected to bring heavy rainfall over parts of southwestern Mexico, possibly concentrated along the coast of Jalisco and in parts of Michoacan, Colima, and Nayarit.

Forecasters warned of life-threatening flooding and mudslides.