“We thought we were safe,” said a spokeswoman for Collier County who declined to give her name because she was not authorized to discuss the situation. “We thought we were safe like 36 hours ago.”
The spokeswoman said that a forecast at 5 p.m. on Thursday caused county officials to react, getting shelters ready and helping residents seeking to evacuate.
Starting on Saturday morning, lines that were several blocks long formed outside shelters such as the Germain Arena, as residents jammed inside.
In Fort Myers, which is in Lee County, buses that were taking people to shelters stopped running at 3 p.m. to allow the drivers to seek safety, potentially stranding people who had not left their homes in time.
Late Saturday afternoon, all the shelters in Collier County were at capacity, according to local news reports. Because of the imminent storm surge, officials told people living in one-story homes to try to enter shelters anyway, and people in two-story homes to seek shelter upstairs.
In Miami-Dade County, some people who had flocked to shelters were reassessing their situation on Saturday afternoon after learning that the brunt of the hurricane would most likely be felt farther west.
“We’re going home,” Virginia Lopez, an administrative assistant at Barry University, said as she loaded her 5-year-old poodle mix, Princess, into her Mazda outside a shelter at Highland Oaks Middle School after spending the night there with her daughter and son-in-law.
“We decided half an hour ago. The storm has moved to Tampa, so we’re going to get a lot of rain but it won’t be as bad. I don’t feel so scared.”
Inside, dozens of people lay on cots and blankets in the building’s hallways amid a stench of perspiration and vomit. Some were packing to leave but most seemed resigned to remaining until the storm blew through.
As Hurricane Irma steered its way toward the Florida Keys on Saturday night, Florida began to feel its approach. The ocean began rising in Key West, spilling into hotel parking lots and roads. In the Keys to the north, water levels toppled over the banks of canals.
In Miami-Dade, tree branches tumbled and fast-moving bands of powerful rain and wind occasionally made it hard to walk. Orange County issued a mandatory evacuation for all mobile homes.
In Lake Worth in Palm Beach County, a tornado tore through one neighborhood, bringing the telltale freight train rumble and clatter of intense wind. On South Beach, palm trees tilted in the wind, their palm fronds fluttering fiercely.
But these ominous signs of Irma’s churn toward Florida were often short-lived. The storm was still far offshore and not expected to be within striking distance of the Keys until the predawn hours.
In the Florida Keys, emergency officials girded for a direct hit and residents who did not evacuate began to take cover as the winds kicked up sharply Saturday afternoon.
The Keys, a thin chain of low-lying islands, are especially vulnerable to Hurricane Irma’s anticipated powerful tidal surges.
The ocean is expected to rise and hurtle into buildings and houses near the coast. Pine Island, north of Key West, was already seeing rising seas at noon.
Some canals were spilling their bounds and emergency responders were evacuating to the Upper Keys.
But the worst could come after the hurricane moves on. Keys residents could find themselves isolated from the mainland if any of the 42 bridges gets damaged.
Residents and emergency officials would be cut off from food, gas and other supplies because there would be no easy way of reaching them by road.
“Just think about the Keys for a second,” Mr. Scott warned residents at a recent news conference. “If we lose one bridge, everything south of the bridge, everybody’s going to be stranded. It’s going to take us a while to get back in there to try to provide services.”
Hurricane Irma has already disrupted Florida’s health systems. As of Saturday night, 29 hospitals, 239 assisted-living centers and 56 other health care facilities in the state were evacuated, according to Jason Mahon, a public information officer at the Florida State Emergency Operations Center. More than 60 shelters were opened for people with special needs.
Not all health organizations made the difficult choice to transfer their patients out of Irma’s path. Tampa General Hospital, the highest-level trauma center in the region, remained open and full of patients and staff, despite being surrounded by water on the tip of Davis Islands.
A spokesman for the hospital, John Dunn, said by phone Saturday night that staff members had arrived on Friday to stay through the storm and work in shifts to care for the hospital’s approximately 700 patients.
Mr. Dunn said the hospital had submarine doors to protect against flooding, and generators had been elevated from the ground floor to a higher level. They are capable of powering air-conditioning for parts of the buildings, he said.