The wind uprooted trees and peeled off roofs; coastal waters resembled a churning hot tub.
"Those folks are getting pounded, and they've got worse to come," said Max Mayfield, director of the National Hurricane Center.
Frances brought with it the potential for more than a foot of rain, tornadoes and heavy flooding.
The storm's slow-motion assault - Frances crawled toward Florida at just 5 mph before stalling for a time over warm water - came more than a day later than predicted.
En route to Florida, Frances shattered windows, toppled power lines and flooded neighborhoods in the Bahamas, driving thousands from their homes. The Freeport airport was partially submerged in water.
Frances' arrival came three weeks afterkilled 27 people and caused billions of dollars in damage in southwestern Florida.
For some Floridians, the second storm couldn't arrive soon enough.
"I just want it to be quick. Just get it over with," said Woodeline Jadis, 20, tired of waiting at a shelter in Orlando.
The storm's outer bands pounded the Florida coast Saturday, and about 300 miles of coastline remained under a hurricane warning.
Frances was so big, twice as large as the devastating Hurricane Andrew in 1992, that virtually the entire state feared damage from wind and heavy rain. Forecasters said the storm would dump 8 to 12 inches of rain, with up to 20 inches in some areas.
"This is the time to show some resolve and not be impatient," Gov. Jeb Bush said. "This is a dangerous, dangerous storm."
"This is going to be a tough ride for us over the next few days," he said.
CBS News Correspondent Dan Rather, in West Palm Beach, emphasized, "The big story here is the water: The storm's plodding pace could cause disastrous flooding."
State meteorologist Ben Nelson said Frances might remain over Florida for two cycles of high tide, meaning two rounds of storm surges expected to be 4 to 6 feet north of where the eye hits.
"The water has nowhere to go and gets trapped because our elevation is so low," he said. "It could be a large mess."
The Federal Emergency Management Agency director Michael Brown warned that unlike Charley, Frances "has an awful lot of moisture with it" that could cause dangerous floods.
"It is a massive storm," Brown said Saturday.
The largest evacuation in state history, with 2.8 million residents ordered inland, sent 70,000 residents and tourists into shelters.
The storm shut down much of Florida, including airports, amusement parks and the Kennedy Space Center, at the start of the usually busy Labor Day weekend.
Some evacuees, frustrated by Frances' sluggish pace, decided to leave shelters Saturday and return later.
Deborah Nicholas dashed home from a Fort Pierce shelter to take a shower, but stayed only a few minutes when the lights started flickering and trees began popping out of the ground. She has slept in a deck chair at a high school cafeteria since Wednesday.
"I'm going stir crazy," Nicholas said. "I'm going to be in a straitjacket by Monday. I don't know how much longer I can take it. Have mercy."
Ron and Virginia Pastuch went home after spending two days at a Palm Bay shelter. Pastuch said he had never been in a shelter before.
"It's the first time, and the last time, too," he said.
Residents could take comfort that Frances weakened as it lingered off the coast. Forecasters downgraded it to a Category 2 hurricane as sustained winds receded to 105 mph, down from 145 earlier.
But in Vero Beach, CBS News Correspondent Mark Strassman said winds were so strong, it was a struggle just to stand.
In Stuart, at least a dozen businesses along U.S. 1 were damaged as the eye approached. Traffic lights dangled, and one hung by a single wire. Downed trees blocked at least one street in a residential area, and posts holding road signs were bent to the ground. The facade at a flooring store collapsed, as did the roof of a storage shed at a car dealership.
Wind gusts reached 91 mph at Jupiter Inlet north of West Palm Beach. Florida Power & Light pulled crews off the streets because of heavy wind, meaning 1.1 million customers - businesses and about 2 million people - would have to wait until the storm subsided for power to be restored, utility spokesman Bill Swank said.
Roads, streets and beaches were mostly deserted - the occasional surfer notwithstanding. Roads were littered with palm fronds and other debris. Businesses were shuttered and even gas stations were closed, their empty pumps covered with shrink wrap.
Not everyone stayed home: Two men were charged with looting for trying to break into a Brevard County church.
As the weather worsened, a yacht adrift on the Intercoastal Waterway struggled for more than half an hour in choppy water to anchor in West Palm Beach before tying up to a dock. Other boats bobbed like toys.
The storm meant extended vacations for about 10,000 passengers on nine Carnival Corp. ships unable return to Miami's port on schedule. They were expected to arrive late Sunday or Monday.
A U.S. Coast Guard helicopter rescued a man and his cat riding out the storm on a sailboat anchored in Biscayne Bay. At Palm Beach International Airport, the roof and a door were blown off a hangar.
Kevin Palmer, a photographer in Palm Beach County, said the wind blew so hard at his front door that it was making the copper weather stripping around it vibrate and shriek violently.
"It's become our high-gust alarm," Palmer said. "It sets the tone for your ambiance when you've got the rumbling outside, you have this screeching from the weather stripping and you keep wondering if that thumping you just heard is another tree going over or a coconut going flying."
Frances was expected to push across the state as a tropical storm just north of Tampa, weaken to a tropical depression and drench the Panhandle on Monday before moving into Alabama. A tropical storm watch was extended along the Florida Panhandle, from west of St. Marks to Panama City.
The ninth named storm of the season grew stronger Saturday in the far eastern Atlantic. Tropical Storm Ivan was about 1,450 miles east-southeast of the Lesser Antilles with winds of 60 mph.