The storm, currently in the Gulf of Mexico, is projected to make landfall in Florida. If it becomes a hurricane, it would be the first to hit the state since Wilma in 2005. The center of the storm is expected to be near the Florida coast by early Friday.
Residents along the Gulf Coast, pounded by heavy rain on Wednesday in advance of the storm, should be prepared for flooding and storm surges, as Hermine could bring up to 10 inches of rain, or 20 inches in isolated areas, the hurricane center said.
"It is crucial that every Floridian has a plan in place to ensure their families, homes and businesses are fully prepared," Gov. Rick Scott said in declaring the state of emergency for 51 of the state's 67 counties.
Hermine is moving north-northeast at 12 miles per hour, but is expected to gain speed through Thursday. Strong winds from the storm are expected to reach the Florida coast in the panhandle region beginning Thursday night, the hurricane center said. It also warned of dangerous storm surge and flooding along the Gulf Coast that could be life threatening from Aripeka to Indian Pass, which is located in central Florida about 50 miles north of Tampa.
Rising waters could reach up to one to seven feet above ground in certain areas.
Forecasts call for the storm to cross Florida before continuing northeast along the coasts of Georgia and the Carolinas.
As of early Thursday, the storm was about 250 miles south-southwest of Apalachicola and 275 miles southwest of Tampa, according to the National Hurricane Center.
Previously dubbed Tropical Depression Nine, it strengthened into a tropical storm with 40-mph winds Wednesday afternoon. As of early Thursday, its maximum sustained winds were near 60 mph.
Hermine would become a hurricane if its sustained wind speeds top 74 mph.
A hurricane warning was in effect for the area between Suwannee River westward to Mexico Beach, Florida.
Catfish in the front yard
Some places, like Marco Island, were already dealing with high water in the streets, with residents saying they caught catfish in their flooded front yards, CNN affiliate WZVN reported.
"Craziest thing I ever saw," Darrin Palumbo told the station. "We were driving home from school, and the road was flipping around and moving. We finally figured out there was a bunch of catfish flopping around the road."
The town of Largo in Pinellas County experienced heavy flooding, with six families having to move out after water invaded their apartments, CNN affiliate WFTS reported.
People in Spring Hill, in Pasco County, are still recovering from flooding a few months ago, WFTS reported
. That flood made the road they depend on impassable, resident Misty Hale said.
"It's going to be 10 times worse," she said.
Residents have been sharing images of high water running through neighborhoods.
In one video, a man is seen paddleboarding down a street. A photo from Holmes Beach showed a woman floating on an air mattress in her driveway.
In Anna Maria Beach, cars were splashing as they drove through hubcap-high water in the street.
Two Florida counties are taking no chances with its oceanside locales. Franklin County, just southeast of Panama City, issued a mandatory evacuation order for the coastal towns of St. George Island, Dog Island, Bald Point and Alligator Point, the county's emergency management office
Crawfordville Elementary School will open as a shelter at 5 p.m., the county said.
In Taylor County, farther east, evacuation orders were in place for Dekle Beach, Keaton Beach, Dark Island, Cedar Island, Steinhatchee, Spring Warrior, Econfina and Nutall Rise, CNN affiliate WTXL reported
Ten offshore oil and gas platforms in the Gulf of Mexico were also evacuated in anticipation of the storm.
NFL preseason game changed
In Tampa, the Buccaneers' final preseason NFL game against the Washington Redskins was moved from Thursday night to Wednesday in expectation of the storm.
Other parts of Florida are already feeling Hermine's effects. In Pinellas County, the southwest county that is home to Clearwater and St. Petersburg, schools have already been closed for Thursday, and a flood warning is in effect. Nearby Manatee County also closed schools.
The National Weather Service has issued a new online product to help people prepare for the storm.
The storm surge watch/warning graphic
highlights spots with the highest risk for "life-threatening inundation from storm surge," the service said.