NEW MEXICO: Residents of coastal towns in Florida and Alabama boarded up windows and filled sandbags on Friday as Hurricane Isaias bore down on the US Gulf Coast, bringing life-threatening storm surges and winds of 185 kph.

Tens of thousands of people in Florida's Panhandle and along Alabama's Gulf Coast faced mandatory evacuation orders. Local television stations showed roads packed with vehicles heading north, away from the water.

The Category 3 Isaias, the first hurricane of an unusually quiet season for the United States, was expected to make landfall between Mobile, Alabama, and Grayton Beach in the Florida Panhandle on Friday evening, according to the National Hurricane Centre.

The 145-kilometre stretch of coast is known for its brilliant white sand beaches, with some areas packed with holiday homes next to small coastal towns such as Destin, Florida.