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Rivers in Florida and Alabama are rising Thursday after Hurricane Sally blasted the region, leaving at least two dead as the storm's remnants spread the threat of flooding and tornadoes across the Southeast.

The National Weather Service (NWS) forecast office in Mobile, Ala., said rivers in the Florida Panhandle and parts of Alabama continue to rise from all the rain, with several at major flood stage.

"Rivers in Alabama continue to rise especially in Escambia county Alabama near Brewton," the NWS said.

SALLY SPREADS 'TORRENTIAL' RAINS OVER SOUTHEAST, TEDDY TO BECOME MAJOR HURRICANE ON WAY TO BERMUDA

At a news conference Wednesday, Florida Gov. Ron DeSantis warned residents and visitors in flooded areas that they would need to remain vigilant as water from the hurricane subsides because heavy rains to the north were expected to cause flooding in Panhandle rivers in coming days.

Floodwaters move on the street, Wednesday, Sept. 16, 2020, in Pensacola, Fla. Hurricane Sally made landfall Wednesday near Gulf Shores, Ala., as a Category 2 storm, pushing a surge of ocean water onto the coast and dumping torrential rain. (AP Photo/Gerald Herbert)

“So this is kind of the initial salvo, but there is going to be more that you’re going to have to contend with,” DeSantis said.

DeSantis added Wednesday that nearly 600 search-and-rescue missions have been conducted in Northwest Florida. The governor was set to visit Pensacola on Thursday.

Local officials have been warning the region faces a second round of flooding in the coming days from rivers and creeks swollen by the storm's heavy rains.

“We are not out of the woods yet,” said Escambia County emergency manager Eric Gilmore.

Storm damaged boats sit at the dock in a marina, Thursday, Sept. 17, 2020, in Pensacola, Fla. (AP Photo/Gerald Herbert)

In hard-hit Pensacola and surrounding Escambia County, where Sally's floodwaters surged through downtown streets and lapped at car door handles on Wednesday before receding, authorities went door-to-door to check on residents and warn them the danger wasn't over.

Sally roared ashore early Wednesday near Gulf Shores, Ala., as a Category 2 storm packing winds of 105 mph but moved slowly through the area, exacerbating heavy rainfall.

Up to 30 inches of rain fell in Bellview, Fla., while other areas saw over 20 inches of rain.

Roadways across Florida's Panhandle were washed out by heavy rain from Hurricane Sally. (Walton County Sheriff's Office)

Local authorities said hundreds of people have been rescued across Florida and Alabama as first responders fanned out in floodwaters. Numerous roads remain washed out and closed.

The Walton County Sheriff's Office said one of the rescues on Wednesday included a senior citizen who called dispatch after being stuck on the second floor by floodwaters with his oxygen running out.

“The water so high, we figured the best way we could try to assist him was with a kayak,” Deputy Carla O’Dell said in a news release. “If we waited any longer it would have been up to our chest.”

HURRICANE SALLY: MASSIVE ALLIGATOR CAPTURED SWIMMING IN ALABAMA STORM SURGE

O'Dell and Deputy Keith Parsons, along with a good Samaritan, waded out into the flooded home to quickly getting the senior to higher ground.

A man who was running out of oxygen was rescued from his flooded home after Hurricane Sally made landfall on Wednesday, Sept. 16, 2020. (Walton County Sheriff's Office)

“I think he was just shocked at how quickly the water rose,” O’Dell said. “I’m glad we could get to him when we did.”

At least one death was blamed on the storm in Alabama. Orange Beach Mayor Tony Kennon told The Associated Press one person in the popular vacation spot died and another was missing as a result of the storm.

He said he couldn't immediately release details.

A boat is washed up near a road after Hurricane Sally moved through the area, Wednesday, Sept. 16, 2020, in Orange Beach, Ala. (AP Photo/Gerald Herbert)

The city declared a nightly curfew until further notice as long as power is not available and bridges remain closed to nonresidents.

"Stay off the roads and be at your destination before dark as downed power lines, potential gas leaks, debris on roads exist," the city said on Facebook.

Kennon said the damage was worse than that from Hurricane Ivan, which hit 16 years to the day earlier. In a Facebook briefing, Kennon said distribution points would be established Thursday for water, ice and tarps.

“It was an unbelievably freaky right turn of a storm that none of us ever expected,” Kennon said of Sally.

Orange Beach resident Jimmy Oswalt, who rode out the storm, told FOX10 he had a scary night and wouldn't do it again.

"When they say hurricane, get out," he told FOX10.

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Jenni Guerry, deputy director of emergency management for Baldwin County, said the county just east of Mobile Bay sustained “tremendous damage” from the storm.

At a Thursday news briefing, she said search crews have been trying to make sure people are accounted for and taking them to safety when needed.

The business of Joe and Teresa Mirable after Hurricane Sally moved through the area, Wednesday, Sept. 16, 2020, in Perdido Key, Fla. (AP Photo/Gerald Herbert)

In the storm's aftermath, officials said Pensacola International Airport remains closed and officials say they need to assess the safety of the runway and its facility before it reopens.

The airport typically has dozens of daily flights from airlines that include Delta Air Lines, American Airlines, Southwest Airlines, United Airlines and Frontier Airlines. It’s asking passengers to contact their airlines about canceled flights.

Over 540,000 customers remain without power in Alabama, Florida and Georgia as the remnants of Sally move north.

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Sally weakened to a tropical depression late Wednesday and picked up speed. By early Thursday, it was producing torrential rains over eastern Alabama and western and central Georgia.

Forecast rainfall through Friday from Sally. (Fox News)

A second storm-related death was reported in Atlanta after a tree fell on a home.

The Atlanta Fire Department said three people were trapped by the large tree that tumbled onto the house.

Firefighters were able to rescue one person and found a second person who was able to free themselves, FOX5 reported.

The body of the third person was later found inside the structure after firefighters were able to shore up the home.

Up to 6 inches of rain is also possible across parts of Georgia as the remnants of Sally move north, while the Carolinas could see up to 10 inches of rain in some locations.

Forecasters say tornadoes are possible Thursday across southern Georgia and northern Florida.

Flood advisories stretch through the Southeast as Sally treks inland. (Fox News)

Like the wildfires raging on the West Coast, the onslaught of hurricanes during the 2020 Atlantic hurricane season that will soon run out of names has focused attention on climate change, which scientists say is causing slower, rainier, more powerful and more destructive storms.

Fox News' Janice Dean and the Associated Press contributed to this report.