Fierce winds and rain from Tropical Storm Hermine slammed Florida's northern Gulf Coast on Friday and power outages left tens of thousands of households in the dark.

Hermine hits Florida hard0:42

Florida Gov. Rick Scott said the former Category 1 hurricane — which by early Friday morning had weakened to a tropical storm — has so far killed one man, and told residents to stay indoors until it had passed.

Hermine made landfall shortly after midnight about 10 kilometres southeast of St. Marks, bringing heavy rains and packing winds of 130 km/h. It left 70,000 households in the state capital Tallahassee and thousands more elsewhere without power. Scott said a homeless man died in northern Florida when a tree fell on him. 

'It is a mess… we have high water in numerous places.' — Cedar Key Police Chief Virgil Sandlin

In Tallahassee, Mayor Andrew Gillum said power outages are "pretty ubiquitous" and that three-quarters of the city customers didn't have electricity.

Gillum estimated as many as 100,000 local residents are without electricity, including 70,000 city customers.

Widespread flooding inundated communities in northern Florida before the storm reached into Georgia, where conditions were expected to deteriorate throughout the early morning on Friday.

"It is a mess ... we have high water in numerous places," Virgil Sandlin, the police chief in Cedar Key, Fla., told the Weather Channel.

The National Hurricane Center warned that some areas along Florida's northern Gulf Coast may experience three metres of flooding.

'Stay indoors'

Pasco County reported crews rescued 18 people and brought them to shelters after their homes were flooded in Green Key and Hudson Beach early on Friday.

"Stay indoors even if it is calm outside. The eye of Hermine may be passing through. Let it pass completely before surveying any damage," Gov. Scott advised residents in a Twitter post.

The National Weather Service issued several tornado warnings and watches for communities throughout northern Florida and Georgia on Friday. 

The National Hurricane Center extended a tropical storm watch north through Sandy Hook, New Jersey.

Hermine became the fourth hurricane of the 2016 Atlantic storm season. By 11 p.m. ET, maximum winds were listed at 130 km/h, with hurricane-force winds extending up to 75 kilometres from the storm's centre.

Hermine could dump as much as 51 centimetres of rain in some parts of the state. Ocean storm surge could swell as high as 3.6 metres.

APTOPIX Tropical Weather Hermine

A news reporter doing a stand up near a sea wall in Cedar Key, Fla., is covered by an unexpected wave as Hermine neared the Florida coast, on Thursday. (John Raoux/Associated Press)

State of emergency in 51 counties

Scott declared a state of emergency in 51 of Florida's 67 counties, and at least 20 counties closed schools.

Mandatory evacuations were ordered in parts of five counties in northwestern Florida, with voluntary evacuations in at least three more counties.

Twenty emergency shelters were opened across the state for those displaced by the storm.

"This is life-threatening," Scott told reporters on Thursday.

APTOPIX Tropical Weather Florida

Andre Anton has been gathering his family's belongings as the rain pours inside of his home after a large tree crashed through the roof Wednesday in Tampa, Fla. (Octavio Jones/Tampa Bay Times via AP)

In coastal Franklin County, people were evacuated from barrier islands and low-lying shore areas.

"Those on higher ground are stocking up and hunkering down," Pamela Brownlee, the county's emergency management director, said.

After battering coastal Florida, Hermine was expected to weaken and move across the northern part of the state into Georgia, then southern U.S. coastal regions on the Atlantic, posing a Labour Day weekend threat for tens of millions of people.

On its current path, the storm also could dump as much as 25 centimetres of rain on coastal areas of Georgia, which was under a tropical storm watch, and the Carolinas.

Forecasters warned of "life-threatening" floods and flash floods there. The governors of Georgia and North Carolina on Thursday declared emergencies in affected regions. In South Carolina, the low-lying coastal city of Charleston was handing out sandbags.

APTOPIX Tropical Weather Hermine Florida

Hannah Coles, 9, takes a break from riding her bike to feel a strong rain Thursday afternoon in Gulfport, Fla. ((John Pendygraft/Tampa Bay Times via Associated Press)

With files from Associated Press