Hurricane Helene is strengthening and expected to be a “major” hurricane — at least Category 3 or potentially Category 4 — when it reaches Florida’s Big Bend tomorrow, the National Hurricane Center said in its latest advisory.

Parts of the Florida coast could get storm surge of up to 20 feet.

Helene is about 460 miles southwest of Tampa, Florida, and moving north at around 12 mph. The storm is expected to cross the eastern Gulf of Mexico tonight and make landfall tomorrow evening, according to the NHC.

The hurricane has maximum sustained winds near 85 mph, with higher gusts, the advisory said. Significant rain, high winds and dangerous storm surge are all expected as Helene approaches the Gulf Coast.

Helene is expected to dump 4 to 8 inches of rain over western Cuba, the Cayman Islands and the northeast Yucatán Peninsula before it reaches the U.S. Across the Southeast, the storm could produce 6 to 12 inches of rain, with isolated totals around 18 inches, causing “catastrophic and potentially life-threatening flash and urban flooding,” the NHC said.

After it makes landfall, the storm is expected to turn northwest and slow down over the Tennessee Valley on Friday and Saturday, according to the advisory.

Though the storm is expected to weaken after landfall, its strong, damaging winds are expected to “penetrate well inland across the southeastern United States, including over the higher terrain of the southern Appalachians,” the NHC said.

Florida Gov. Ron DeSantis offered a reminder to owners of electric vehicles as they prepare for Hurricane Helene: “If you have an EV, you need to get that to higher land,” he said. “Be careful about that getting inundated. It can cause fires.”

At a news briefing this afternoon, he said such fires have become more common in Florida in recent years.

“You’re in an area that is in the eye of where there can be storm surge, you have an electric vehicle — just know that when you have saltwater intrusion on that, those can catch on fire,” DeSantis said. “Those are very difficult to put out.”

Indeed, electric vehicles are powered with banks of lithium-ion batteries that, if they catch fire, can burn for a long time and are very hard to extinguish. Saltwater is highly conductive, which adds extra risk during periods of high storm surge and coastal flooding.

In 2022, after Hurricane Ian hit southwestern Florida, firefighters near Naples responded to six EV fires that burned for “hours and hours” and required “thousands upon thousands” of gallons of water to put out, E&E News reported.

All Atlanta public schools will be closed tomorrow and Friday as a result of “expected severe weather from the impact of Hurricane Helene,” officials said in a statement.

District office employees will work remotely, and an update will be issued Friday afternoon about any activities over the weekend, officials said.

Scientists with the National Oceanic and Atmospheric Administration flew into the center of Hurricane Helene earlier today, capturing video of the storm’s immensity and its expansive clouds.

The researchers, known as “hurricane hunters,” fly through storms to gather data that can improve forecasts and help scientists better understand tropical storms and hurricanes as they develop.

NOAA maintains a fleet of three WP-3D turboprop aircraft — nicknamed Miss Piggy, Kermit and Gonzo — for the bumpy missions.

Mayor Andre Dickens said Atlanta is preparing for impacts from Hurricane Helene, including significant wind, heavy rain and flooding.

In a news conference this afternoon, Dickens said agencies are clearing drain systems to prepare for the rain, given that the city’s topography can put it at risk for serious flooding.

“We’re a city of 1,000 hills, as it’s been called before,” he said. “And those low-lying areas are bowls.”

Crews are also ready to deal with downed trees, Dickens added, and shelters are open for people who need housing.

Florida Gov. Ron DeSantis said people in the state should anticipate widespread power outages, heavy rain and high winds as Hurricane Helene approaches.

The fast-moving storm is expected to bring 12 inches of rain over parts of the state, DeSantis said at a news briefing, and storm surge could reach up to 15 feet in some areas.

“Just know these effects are coming to the state of Florida, and it’s not a matter of whether we’re going to get effects, it’s just a question of how significant those effects will be,” he said.

A state of emergency is in effect as Florida braces for the hurricane to make landfall tomorrow in the Big Bend region, potentially as a Category 3 storm.

“The eye of the storm is coming in this region,” DeSantis said.

State officials emphasized that it’s not too late to evacuate or make preparations, but they warned that people shouldn’t wait any longer.

“You should be finalizing your plans now, executing on your plans,” said Kevin Guthrie, executive director of the Florida Division of Emergency Management. “Tomorrow midday will be way too late.”

South Carolina Gov. Henry McMaster declared a state of emergency today ahead of potential impacts from Hurricane Helene.

McMaster said people in the state should monitor local forecasts and begin taking precautions now.

“Although South Carolina will likely avoid the brunt of Hurricane Helene’s impacts, the storm is still expected to bring dangerous flooding, high winds and isolated tornadoes to many parts of the state,” McMaster said in a statement.

The storm is expected to make landfall in Florida's Big Bend, then bring strong winds, major rainfall, flash flooding and other risks to other southeastern states including South Carolina.

Early forecasts suggest Hurricane Helene could become a major Category 3 storm before it reaches Florida's Big Bend. That intensification is expected to happen quickly as the hurricane moves over warmer-than-usual waters in the Gulf of Mexico.

Warm water is a key ingredient in the formation and development of storms, and warm conditions in the ocean and in the atmosphere can jumpstart the process known as rapid intensification.

The term describes an increase in sustained wind speeds of at least 35 mph over 24 hours, according to the National Hurricane Center.

Many recent storms have undergone rapid intensification before making landfall, including Hurricane Ian in 2022, which strengthened into a Category 3 storm as it neared Florida’s coast. A year before that, Hurricane Ida’s maximum sustained winds increased by 65 mph over a span of just 24 hours. And in 2019, Hurricane Dorian underwent rapid intensification twice before it made landfall in the Bahamas.

Climate change is increasing ocean temperatures, but teasing out what role — if any — that global warming plays in the rapid intensification of storms has been complicated so far. Overall, studies have shown that climate change may not be increasing the total number of hurricanes that form, but it can make the storms that do occur more intense.

Helene is 110 miles north-northeast of Cozumel, Mexico, the National Hurricane Center said in a 2 p.m. advisory. 

It’s expected to take a turn toward the northeast and increase its forward speed later today and tomorrow. That will likely bring Helene’s center across the eastern Gulf of Mexico to Florida's Big Bend coast by tomorrow evening. 

Helene is still forecast to strengthen and become a major hurricane by the time it reaches Florida. 

"Preparations to protect life and property from storm surge and damaging winds along the Florida Big Bend Coast should be rushed to completion today," the NHC warned.