(CNN) -- As some Florida Keys residents return to their devastated islands Tuesday, 15 million Floridians are learning when they'll finally get power back.
All customers who lost electricity on the eastern side of the state will likely have power restored by the end of this weekend, Florida Power & Light said Tuesday.
Customers on the west coast of Florida -- where Hurricane Irma made its final landfall -- will likely have power restored by September 22.
It's a long wait for those sifting through what's left of their homes in the oppressive heat, bombarded by high humidity and relentless mosquitoes.
But residents like William Rose have bigger concerns. Rose still can't reach his family on the Florida Keys, where a quarter of the islands' houses are annihilated.
He's not sure whether his mother, stepdad, grandmother and aunt survived Irma's wrath.
"I have no idea, but I'm trying to stay positive," Rose said.
Before the Keys lost cell phone service, he received a text from his mother, who chose not to evacuate.
"This is terrible. I will never do this again," the text read. "I'm so glad you got out."
Mass destruction in the Keys
Two days after Irma made landfall on Cudjoe Key, authorities and residents were finally able to reach some of the Florida Keys on Tuesday.
What they found was devastating: An estimated 25% of the houses on the chain of islands have been destroyed, the Federal Emergency Management Agency said Tuesday. Another 65% suffered major damage.
"Basically, every house in the Keys was impacted some way," FEMA Administrator Brock Long said.
It's still not clear how many casualties Irma caused on the Keys. Transportation officials are trying to determine whether bridges between the islands can withstand any weight. The Florida Department of Transportation is repairing two sections of road that were washed away by Irma -- one at mile marker 37 and the other at mile marker 75 -- but believe they will finish later Tuesday.
Darwin Tabacco, who stayed on Big Pine Key during Irma, is one of the fortunate residents. Both he and his house survived.
"A lot of people lost everything," he said Tuesday morning. "There's homes blown off the stilts. There's power lines down all over the place. Trees completely uprooted. People's businesses flooded. Septic fields flooding. It's just terrible."
15 million people without power -- just in Florida
Massive power outages are crippling much of the Southeast on Tuesday. Among the hardest hit by Irma:
Florida: About 15 million people are without power across the state, the Department of Homeland Security said Tuesday. Georgia: More than 1.3 million customers -- which includes households and businesses -- are in the dark, according to Georgia Power and Georgia EMC. South Carolina: 161,000 customers lost power, according to Duke Energy and SCE&G. North Carolina: More than 62,000 customers don't have electricity, according to Duke Energy. Alabama: More than 20,000 customers lost electricity, Alabama Power said Tuesday.
9 states impacted
Irma, which stretched 650 miles from east to west, has pummeled at least nine states -- deluging city streets, uprooting trees and destroying homes along the way.
Although Irma is now a tropical depression, it's still expected to bring torrential rainfall as far north as North Carolina on Tuesday.
At least six storm-related deaths have already been reported, according to local officials:
Georgia had three deaths. A 62-year-old man who was on his roof was killed in Worth County, which experienced wind gusts of 69 mph. Another man was killed in Sandy Springs when a tree fell on his house. And a woman was killed when a tree struck her vehicle in Cumming. Florida had two deaths. A driver died in a crash on State Road 417. Another person died in Miami-Dade County from carbon monoxide poisoning after using a generator indoors. South Carolina had one death. A 57-year-old man was struck by a falling tree limb during the storm.
Florida governor: Returning home may be dangerous
Beyond the Keys, Floridians were anxious to return and see how their homes weathered the storm. But officials urged patience.
"Check with local officials before returning home to make sure you can safely do so," said Gov. Rick Scott on Monday.
"Don't think just because this thing passed, you can run home. We've got downed power lines all across the state. We've got roads that are impassible still across the state. We've got debris all over the state."
Flights, hospitals will be back online
While the Keys have an exhaustive recovery ahead, signs of normalcy will pop up Tuesday elsewhere in Florida.
Many of Florida's airports are scheduled to re-open with limited operations Tuesday.
And Florida Hospital, a health provider in the state, said it plans to reopen many of its impacted facilities on Tuesday or Wednesday.
Even a weakened Irma engulfed cities as far north as Charleston, South Carolina, on Tuesday.
"I really didn't expect it to become this bad here," Charleston resident Mike Stusnick said Tuesday. "It came in really fast last night. ... We were just praying that it didn't come all the way into the house, and it didn't."
Jacksonville, Florida -- the largest city by area in the contiguous US -- is still trying to recover from record-breaking storm surge and flooding on Monday.
More than 300 people have been rescued in Jacksonville, the governor said Tuesday.
"So many areas that you thought wouldn't flood, flooded," Scott said.
Irma's deadly trail
Before slamming into the United States, Irma hit Cuba late Friday as a Category 5 hurricane. On Monday, Cuban state TV announced 10 hurricane related deaths -- meaning Irma killed a total of 36 people in the Caribbean before heading to the US.
This is the first year on record that the continental United States has had two Category 4 hurricane landfalls in the same year.
Last month, Hurricane Harvey devastated much of coastal Texas and killed more than 70 people.
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