Hurricane Isaias makes landfall on Florida's Gulf Coast

Hurricane Isaias made landfall on the US Gulf Coast near Destin, Florida, on Friday evening, with sustained winds of up to 165 kilometres per hour, the US National Hurricane Center (NHC) said.

The storm had strengthened to Category 3 on the five-point scale as it crossed the Gulf of Mexico before weakening to Category 2 ahead of landfall.

"The storm is here," Florida Governor Ron DeSantis said at a news conference late on Friday. He urged residents to stay off the roads and wait until the storm had passed.

Meteorologists warned of life-threatening storm surges, heavy rainfall and flooding. Storm surges could raise water levels by up to 2.7 metres above normally dry ground along parts of Florida's north-western coast. Tornadoes were also possible.

States of emergency had been declared in several states, while evacuations were ordered in vulnerable coastal areas of Florida and Alabama. Flights were cancelled and shops and schools closed ahead of the storm. Authorities imposed a nighttime curfew in Mobile, Alabama.

Nearly 500,000 electricity customers in Florida and Alabama were without power late on Friday, according to Poweroutage.us.

DeSantis had earlier warned residents to prepare for prolonged power outages and possible road closures. Residents were advised to stock up on enough supplies to last at least 72 hours without normal services. Emergency management officials mobilized more than 1,000 generators and large fuel reserves, among other resources.

Isaias is the first hurricane of the Atlantic season. It was expected to weaken as it moved inland, although heavy rain, flooding and dangerous wind gusts were forecast in Alabama, Georgia and Tennessee.