Isaias surged toward the U.S. Gulf Coast on Thursday as the first hurricane of the Atlantic season, prompting mandatory evacuations, school closures and local government shutdowns in parts of Florida.

Isaias was forecast to intensify rapidly and bring strong winds and a life-threatening storm surge to the Florida Panhandle, southern Alabama and southern Mississippi when it makes landfall on the northern Gulf Coast late Friday or early Saturday. Heavy rain with the risk of flooding was possible into the weekend as far inland as the Tennessee Valley.

“We are expecting Isaias to be a dangerous hurricane when it makes landfall,” Michael Brennan, director of the National Hurricane Center in Miami, said in a mid-morning update.

The hurricane had maximum sustained winds around 85 mph (140 kph) and was moving east-northeast at 10 mph (17 kph) as of late Thursday morning, the hurricane center said. It was centered about 380 miles (610 kilometers) south of the mouth of the Mississippi River.

Coastal communities moved quickly to prepare. Some Gulf oil wells paused production, and at least four Florida school districts canceled classes for later in the week. Okaloosa County announced mandatory evacuations for some coastal areas, and communities closed government offices as of Thursday afternoon. The governors of Florida and Alabama, meanwhile, declared a state of emergency for dozens of counties.

Dauphin Island, a 15-mile-long barrier island off the Alabama coast, encouraged some people to voluntarily evacuate.

“That area is traditionally very vulnerable to storm surge — salt water flooding — and that is also where most of the visitors are," Mayor Jeff Collier said Thursday of the western part of the island.

He said he didn't anticipate substantial damage, “but at the same time, these things are very fickle and a little jog here or there or some last-minute increase in strength, we just have to be prepared for the worst.”

Water from the storm surge and high tide could reach heights of 5 to 7 feet (1.5 to 2 meters) in parts of Alabama and Mississippi, the hurricane center said. Isaias also could dump up to 10 inches (25 centimeters) of rain along parts of the Gulf Coast and spawn tornadoes overnight Friday into Saturday from Alabama to the Florida Panhandle and southwestern Georgia. The hurricane itself is expected to quickly weaken after making landfall.

The National Weather Service told communities from Ocean Springs, Mississippi, to Gulf County, Florida, to prepare for the possibility of “long-duration power outages.”

The hurricane formed late in the season

Isaias developed more than four months into the Atlantic hurricane season and was short by one day of tying a 121-year-old record for the area’s latest-forming hurricane. According to the weather service, the record dates to 1905, when the year’s first Atlantic hurricane formed on Oct. 8.

The Atlantic hurricane season has been unusually quiet this year because of a strong El Niño, which disrupts storm formation over that ocean. Storm activity has been above average in the Pacific, where Tropical Storm Simon formed Wednesday off Mexico and where Tropical Storm Rachel, formerly a hurricane, was expected to approach the northern Baja California, Mexico, and southern California this weekend, the hurricane center said.

Isaias is expected to strike a swath of coastline that’s familiar with major hurricanes.

One of the 20th century’s worst storms, Hurricane Camille, killed more than 250 people after hitting land near Waveland, Mississippi, in 1969. Hurricane Katrina in 2005 razed neighborhoods in Mississippi, flooded New Orleans and killed nearly 1,400 people. And Hurricane Michael leveled homes and buildings near Panama City, Florida, in 2018.

Oil production and tourism are already affected

Ahead of the storm, oil and gas producers shut down a significant share of offshore production in the Gulf, which accounts for almost 15% of crude pumped annually in the U.S.

As of Wednesday, about 25% of the oil production in the region had been temporarily halted, taking about 511,000 barrels a day off the market, according to the Marine Minerals Administration. It said eight of the Gulf's 371 manned oil platforms had been evacuated.

With oil prices already high, the production cuts are steep enough to affect markets, though other Gulf hurricanes have caused larger disruptions, said Jim Burkhard, global head of crude oil market research for S&P Global Energy. More concerning, he said, is whether Isaias strikes as a powerful storm near refineries.

As it moves inland, Isaias might also disrupt Saturday’s college football showdown between rivals Georgia and Alabama, a game President Donald Trump has planned to attend.

In Gulf Shores, an Alabama community encouraging voluntary evacuations, resident Maranie Adams gathered water and other supplies as her family moved belongings, including a hot tub motor, to higher ground. Her family planned to ride out the storm at home, roughly a half-mile from shore, sheltering indoors alongside their flock of chickens.

“We’re having to get crates to bring them into the house so they don’t blow away,” Adams said. “It’s going to be noisy.”

Alabama Gov. Kay Ivey issued a state of emergency for 40 counties, while Florida Gov. Ron DeSantis declared one for 25 counties in the Panhandle and Big Bend regions. The state also planned to deploy a Miami-based urban search and rescue task force.

In Pensacola, electric utilities were pre-positioning crews to quickly repair any power outages. City officials provided sand for residents to fill sandbags to protect their homes against flooding. And Mayor D.C. Reeves urged people to check on older adult neighbors and others who might need help.

“Obviously no need to panic at this point,” Reeves told a news conference. “This is really about preparation.”

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Associated Press reporters Kathy McCormack, Kim Chandler, Russ Bynum and Julie Walker contributed to this report.