Charley, which strengthened rapidly into a rare and powerful Category 4 storm - the second strongest on a scale used to rate hurricanes - roared ashore on Friday over the resort island of Captiva off southwest Florida, further south than expected.
It swamped the vulnerable shoreline with a wall of water up to 4.5m high, then barrelled inland over Port Charlotte, gouging a broad swathe of destruction.
"The early indications are that this storm has had a devastating impact on our state and people need to take it very seriously," Florida Governor Jeb Bush said after the hurricane made landfall.
Bush said it was still early to make a damage assessment, but "as the storm passes teams will come into the community to do so".
Bush called hurricanes like Charley "one of God's most formidable forces".
Officials urged at least 1.4 million Floridians to flee before the storm - one of the largest peacetime evacuations in US history. The mandatory evacuation orders, however, were widely ignored.
In Florida, at least two people died in traffic accidents during the storm and more than 350,000 people across the state lost power.
"Right now, its mass damage," said a city administrator in the town of Arcadia, one of the hardest-hit areas.
The hurricane ripped the roof off a town area being used as an emergency shelter for 1500 people.
Earlier, Hurricane Charley battered Cuba for more than two hours, tearing roofs off houses, ripping up trees and cutting power. At least three people were killed by the storm.
About 215,000 residents and 2000 tourists were evacuated from high-risk areas in western Cuba before the storm passed ahead.