MIAMI (AP) — Tropical Storm Debby strengthened rapidly Sunday and was expected to become a hurricane as it moved through the Gulf of Mexico toward Florida, bringing with it the threat of devastating floods to the southeast Atlantic coast later in the week.

The storm was likely to become a Category 1 hurricane before making landfall Monday in the Big Bend region of Florida, the National Hurricane Center in Miami said.

From there, the storm is expected to move eastward over northern Florida and then stall over the coastal regions of Georgia and South Carolina, drenching the region with the potential of record-setting rains totaling up to 30 inches (76 cm) beginning Tuesday.

“There’s some really amazing rainfall totals being forecast and amazing in a bad way,” Michael Brennan, director of the National Hurricane Center in Miami, said at a briefing Sunday. “That would be record-breaking rainfall associated with a tropical cyclone for both the states of Georgia and South Carolina if we got up to the 30 inch level.”

The flooding impacts, which could last through Friday, are expected to be especially severe in low-lying areas near the coast, including Savannah, Georgia; Hilton Head, South Carolina; and Charleston, South Carolina.

The hurricane center said in an update posted at 11 a.m. Sunday that Debby was located about 130 miles (210 kilometers) west-southwest of Tampa, Florida, and about 160 miles (260 kilometers) south-southwest of Cedar Key, Florida. The storm was moving north-northwest at 13 mph (21 kph) with maximum sustained winds of 65 mph (105 kph), up from 50 mph (80) just a few hours ago.

Officials also warned of life-threatening storm surge along Florida’s Gulf Coast, with 6 to 10 feet of inundation expected Monday between the Ochlockonee and Suwannee rivers.

“I’d urge all Floridians to be cognizant of the fact that we are going to have a hurricane hit the state, probably a Category 1, but it could be a little bit more powerful than that,” Florida Gov. Ron DeSantis said in a Sunday morning briefing.

“But we are absolutely going to see a lot of rainfall. We are going to see a lot of saturation. We are going to see flooding events,” he said. “There is also going to be power outages.”

DeSantis said that, for the first time, constructed flood control devices are being placed at utility stations to try to minimize the risk of power interruptions because of flooding.

“We think that is going to be able to mitigate some of the power outages,” DeSantis said.

Meanwhile, wind and thunderstorms have spread over a broad area including southern Florida, the Florida Keys and the Bahamas.

Debby is the fourth named storm of the 2024 Atlantic hurricane season after Tropical Storm Alberto, Hurricane Beryl and Tropical Storm Chris, all of which formed in June.

The National Hurricane Center in Miami predicted the system will strengthen as it curves off the southwest Florida coast, where the water has been extremely warm.

A hurricane warning was issued for parts of the Big Bend and the Florida Panhandle, while tropical storm warnings were posted for Florida’s West Coast, the southern Florida Keys and Dry Tortugas. A tropical storm watch extended farther west into the Panhandle. A warning means storm conditions are expected within 36 hours, while a watch means they are possible within 48 hours.

Tropical storms and hurricanes can trigger river flooding and overwhelm drainage systems and canals. Forecasters warned of 6 to 12 inches (150mm to 300 mm) of rain and up to 18 inches (450 mm) in isolated areas of Florida, which could create “locally considerable” flash and urban flooding. Forecasters also warned of moderate flooding for some rivers along Florida’s West Coast.

Storm surge expected to hit Gulf Coast, including Tampa Bay

Flat Florida is prone to flooding even on sunny days, and the storm was predicted to bring a surge of 2 to 4 feet (0.6 to 1.2 meters) along most of the Gulf Coast, including Tampa Bay, with a storm tide of up to 7 feet (2.1 meters) north of there in the sparsely populated Big Bend region.

Forecasters warned of “a danger of life-threatening storm surge inundation” in a region that includes Hernando Beach, Crystal River, Steinhatchee and Cedar Key. Officials in Citrus and Levy counties ordered a mandatory evacuation of coastal areas, while those in Hernando, Manatee, Pasco and Taylor counties called for voluntary evacuations. Shelters opened in those and some other counties.

Citrus County Sheriff Mike Prendergast estimated 21,000 people live in his county’s evacuation zone. Officials rescued 73 people from storm surge flooding during last year’s Hurricane Idalia. Prendergast said by phone that he hopes not to have a repeat with Debby.

“After the storm surge does come in, we simply don’t have enough first responders in our agency and among the other first responders in the county to go in and rescue everybody that might need to be rescued,” he said.

Flood preparations underway

DeSantis declared a state of emergency for 61 of Florida’s 67 counties, with the National Guard activating 3,000 guard members. Georgia Gov. Brian Kemp made his own emergency proclamation on Saturday.

The White House said federal and Florida officials were in touch and FEMA “pre-positioned” resources including water and food.

In Tampa alone, officials gave out more than 30,000 sandbags to barricade against flooding.

“We’ve got our stormwater drains cleared out. We’ve got our generators all checked and full. We’re doing everything that we need to be prepared to face a tropical storm,” Tampa Mayor Jane Castor said.

Florida State University in Tallahassee will be closed Monday due to the storm, the school announced.

On Friday, crews pulled floating cranes away from a bridge construction project across Tampa Bay, lashing together 74 barges and 24 floating cranes and anchoring them, project engineer Marianne Brinson told the Tampa Bay Times. Crews also laid down cranes on land on their sides.

Emergency managers in New England and New York were already monitoring the path of the storm for the possibility of remnants striking their states. States including New York and Vermont have been hit by heavy rain and thunderstorms in recent weeks and were still coping with flooding and saturated ground.

Vermont, in particular, suffered two separate flooding events in July, and another could bring heavy damage to communities still repairing from earlier floods. The July storms came on the heels of “last summer’s flood, destroying infrastructure, homes, and property,” Gov. Phil Scott said Saturday.

For some, the name Debby summons bad memories of a 2012 tropical storm of the same name that caused $250 million in losses and eight deaths, including seven in the Sunshine State. That storm dumped torrential rains, including an astronomical 29 inches (730 mm) south of Tallahassee.