Tropical storm-force winds reached Florida’s western coast on Wednesday afternoon, according to the National Hurricane Center (NHC), as the state prepares for what Joe Biden has called the “storm of the century”. As expected, Hurricane Milton has weakened to a category 3 storm as it makes landfall, but is still a deadly threat, especially to the heavily populated and highly vulnerable communities of Tampa, St Petersburg and Sarasota.

Milton is currently centered about 100 miles south-west of Tampa and is expected to hit the Florida coast late on Wednesday or early on Thursday.

Although wind speeds at the center of the storm have dropped to 125mph (205km/h), seven tornados touched down across the state on Wednesday before the surge, according to the National Weather Service. The entire state remains under tornado watch until 9pm ET, with more than 50 tornado warnings issued and the greatest threat expected “across parts of the central and southern Florida peninsula this afternoon”, according to the National Weather Service.

“Milton has the potential to be one of the most destructive hurricanes on record for west-central Florida,” the NHC warned.

Earlier in the day, the governor of Florida, Ron DeSantis, said it was not clear exactly where the eye of the storm would come ashore but the impact would be “broader than that … absolutely every place on the west coast of Florida could get major storm surge”.

DeSantis later said 8,000 national guard members would be activated and he had spoken with Joe Biden about Florida’s needs. “Everything that we’ve asked for, the administration has approved,” he said.

“If you are in a single-storey home that is hit by a 15ft storm surge, which means that water comes in immediately, there’s nowhere to go,” said the mayor of Tampa, Jane Castor.

“So if you’re in it, basically that’s the coffin that you’re in.”

She added on Wednesday afternoon that she has “never seen an evacuation of this magnitude”.

Deanne Criswell, the director of Fema, said at a news conference that she would travel to Florida on Wednesday – and would send more agency personnel to the state. “I want the people to hear it from me directly: Fema is ready.” Her regional administrator will remain in North Carolina, where recovery efforts from Hurricane Helene are ongoing.

Authorities have issued mandatory evacuation orders across 11 Florida counties with a combined population of about 5.9 million people and said anyone choosing to stay behind must fend for themselves.

Those evacuating are facing growing fuel shortages. According to analysts at GasBuddy, more than 60% of gas stations in Tampa and St Petersburg were without fuel on Wednesday afternoon.

Under current projections, the surge is expected to hit between Tampa Bay and Sarasota, possibly around Bradenton.

The area was also hit by Hurricane Helene two weeks ago, raising concerns that discarded furniture, appliances and debris from that storm will become projectiles in this next one. DeSantis said the state deployed more than 300 dump trucks that had removed 1,300 loads of debris. Before Helene hit, residents staying behind were encouraged to write their name and social security numbers on their bodies for easier postmortem identification.

One resident said he had seen bull sharks swimming in the flooded streets after Helene.

No matter exactly where Milton comes ashore, the damage is expected to be extensive, with seawater funneling up through coastal channels inland. Cody Fritz at the NHC storm surge team told NBC News: “Florida’s west coast is very sensitive to storm surge. It doesn’t take much to push water over land that would be dry. It’s extremely vulnerable.”

Kara Doran, a US geological survey scientist, said the risk of permanent change to the coastline “cannot be overstated as I believe communities are more vulnerable to this storm’s impacts due to the erosion that occurred recently from Helene”.

Residents trying to leave have been faced with gas shortages and gridlocked roads. There are few hotels to shelter in and no flights out of the area. Ashley Khrais, a resident of Holiday, Florida, just inland from the coast, told NBC: “It seems very, very scary, but there’s no way to leave.”

Mark Prompakdee, 71, a resident of a trailer park near St Petersburg, said he planned to sit the storm out in a minivan parked on higher ground at a high school. “They’re saying, ‘Get out of here,’” he said. “Where?”

But many people appeared to have heeded the warnings. “If there’s any good news here, we toured Fort Myers Beach yesterday [and] it looks like people have listened to those warnings,” said Jay Gray of NBC News.

Efforts to protect property with sandbags and by boarding up windows had been done “with the knowledge that this could be the most powerful storm many in this area have ever seen, and they’ve seen plenty”, Gray said.

With area airports now closed, operators said they would not reopen until damage had been assessed. A spokesperson for Tampa international airport told Scripps News that safety was critical for their operations and it could not act as a shelter for travelers stuck there since it is located in an evacuation zone.

Disney World, which had remained open much of Wednesday, announced that its Orlando theme parks would be closed on Thursday.

Across the Caribbean, Milton is causing flooding in low-lying areas of Cuba’s capital city, Havana.