Hurricane Dorian powered toward Florida with increasing fury Friday, growing to an "extremely dangerous" Category 4 storm, according to the U.S. National Hurricane Center, as it menaced the state's eastern coast.

At 8:30 p.m. ET, Dorian was about 645 kilometres east of the northwestern Bahamas, packing maximum sustained winds of 215 km/h, the NHC said.

The storm began Friday over the Atlantic at Category 2, but was upgraded to Category 3 later in the day, with sustained winds of at least 185 km/h.

The entire state of Florida is under a declaration of emergency and Gov. Ron DeSantis has activated 2,500 National Guard troops, with another 1,500 on standby.

Forecasters predict the storm will grow more ferocious as it slows its advance across the warm waters near the coast, striking land late on Monday or early Tuesday. Tropical storm winds could be felt in Florida as soon as Saturday evening.

<a href="https://twitter.com/hashtag/Dorian?src=hash&ref_src=twsrc%5Etfw">#Dorian</a> has strengthened to an extremely dangerous category 4 hurricane. For details go to:<a href="https://t.co/PVkIJ0K5Oc">https://t.co/PVkIJ0K5Oc</a> —@NHC_Atlantic

The Orlando International Airport said in a statement on Friday that it plans to cease flight operations on Monday at 2 a.m. ET as a precaution.

No evacuations were ordered as of early Friday, but they're expected as the storm's path become clearer before it makes landfall.

Recent weather models from the Miami-based NHC show it smacking into the centre of the state. It was trending slightly south in the latest advisory issued at 5 a.m. Friday.

It could roll inland toward Orlando on Tuesday or early Wednesday, weakening as it moves away from the sea. Other NHC weather models show it tracking south toward Miami before it hits the peninsula, or heading north to the Georgia coast.

Along with the dangerous winds, the storm is expected to drop 12 to 25 centimetres of rain on the state, with some areas getting as much as 38 centimetres.

"This rainfall may cause life-threatening flash floods," NHC forecasters said.

U.S. President Donald Trump cancelled a trip to Poland, sending Vice-President Mike Pence in his place, to ensure resources are properly directed for the storm.

"Now it's looking like it could be an absolute monster," Trump said in a video posted on Twitter, adding that food and water were being shipped to Florida.

Hurricane Dorian looks like it will be hitting Florida late Sunday night. Be prepared and please follow State and Federal instructions, it will be a very big Hurricane, perhaps one of the biggest! —@realDonaldTrump

Former Canadian prime minister Kim Campbell issued an apology on Friday after tweeting on Wednesday that she was "rooting for a direct hit on Mar-a-Lago," in reference to Trump's resort in Florida and Dorian's path.

The tweet had sparked fierce social media backlash.

Campbell, a frequent and vocal critic of Trump, has since deleted the offending post, and later tweeted it was "intended as sarcasm — not a serious wish of harm."

I have deleted my tweet about the hurricane & Mar a Lago and sincerely apologize to all it offended. It was intended as sarcasm-not a serious wish of harm. Throwaway lines get a life of their own on Twitter. I shd know better. Mea culpa. —@AKimCampbell

DeSantis said on Friday that local officials are determining evacuation plans.

During the morning briefing, DeSantis said while the precise path of the storm is still uncertain, there is a "high degree of certainty" Dorian will be a major hurricane.

Florida Gov. Ron DeSantis addressing media as Hurricane Dorian approaches the state. (Reuters )

Authorities are urging residents to heed any evacuation orders and be prepared for a "multi-day event," DeSantis said during a news conference.

He also tweeted that people in Florida need to take the storm seriously: "Hurricane #Dorian is moving slowly & gaining strength. Now is the time to get prepared & have a plan."

Georgia Gov. Brian Kemp declared a state of emergency in 12 counties to assist with storm readiness, response and recovery.

'Not looking good'

Angela Johnson, a 39-year-old bar manager in South Florida, said on Thursday: "We're worried. This is not looking good for us.

"We woke up a lot more scared than we went to bed last night, and the news is not getting any better," said Johnson, who manages Coconuts On The Beach, a bar and restaurant on the surfing beach in the town of Cocoa Beach.

Officials were making piles of sand available for Cocoa Beach residents to fill sandbags starting on Friday.

Dorian could churn across dozens of launchpads owned by NASA, the U.S. Air Force and companies such as Elon Musk's SpaceX and Jeff Bezos's Blue Origin.

Category 1-strength winds bend palm trees as Hurricane Dorian slams into St. Thomas, U.S. Virgin Islands, on Wednesday in this still image taken from social media video. (Cassandra Crichlow/Reuters)

CoreLogic, a property information and analytics provider, estimates around 668,000 homes along the east coast of Florida are in the path of Dorian's cone.

It said "$144.6 billion are at potential risk of storm surge damage from Hurricane Dorian based on its projected Category 3 status at landfall."

Hurricane-driven storm surge can cause significant property damage when high winds and low pressure cause water to amass inside the storm, releasing a powerful rush over land when the hurricane moves onshore, the company said.

Gas stations run dry

Some gas stations in Florida have run dry and others have long lines of cars, DeSantis said, adding that the state had eased regulations to allow higher-capacity trucks to transport fuel and to make it easier to bring in fuel from other states.

Gasoline prices at the pump are not expected to spike because of the storm, said Patrick DeHaan, head of petroleum analysis at GasBuddy.com.

Local residents form a queue to fill their cars with gas ahead of the arrival of Hurricane Dorian in Kissimmee, Florida, U.S. August 29, 2019. (Gregg Newton/Reuters)

"This is not going to be a pricing event," DeHaan said. "There are no refiners in Florida. There's only a pipeline, and I can't imagine that would be affected significantly. Fuel is flowing, and that's the most important factor."

"We're also going to be starting today implementing Florida Highway Patrol escorts for fuel trucks so we can increase fuelling in critical parts of the state," he said.

Colonial Pipeline, which delivers fuels such as gasoline and diesel from the Gulf Coast to markets across the southern and eastern United States, said it was operating normally. It had no plans to shut down ahead of Dorian's projected landfall.

Florida officials also were making sure all nursing homes and assisted living facilities had generators, and were checking with 107 facilities where information about generators was uncertain.