By Steve Almasy and Faith Karimi, CNN

(CNN) -- Hurricane Irma may be gone, but days of darkness and devastation are just beginning in Florida.

Residents could go for days without power after the storm uprooted homes, trees and power lines, leaving 4.4 million customers without electricity statewide in simmering temperatures, officials said.

"Temperatures will be around 90 for many, especially central and southern Florida for the next several days," CNN meteorologist Taylor Ward said. "High humidity will make it feel like the low to mid-90s. While it isn't above normal, it's certainly warm and humid which is miserable without power."

Before making landfall in the Florida Keys, the hurricane killed 38 people in the Caribbean islands. At least 17 storm-related deaths have been reported on the US mainland, according to officials.

As Irma left Florida and marched across the southeast this week, it knocked out power in Georgia, Alabama, South Carolina and North Carolina. With the sweltering temperatures, restoration of power is crucial, Florida Gov. Rick Scott said.

"After visiting shelters this week and talking to people who evacuated due to Hurricane Irma, the number one thing I heard from families is that they want their power back on," Scott said.

Customers who lost electricity on the eastern side of Florida will likely have power restored by this weekend because fewer electrical poles came down in the storm than in other parts of the state, Florida Power & Light said Tuesday.

Customers on the west coast of Florida, where Hurricane Irma made landfall, will likely have power restored by September 22, according to the company.

The company is focusing on first restoring power at schools, hospitals and other critical infrastructure.

"While FPL has invested nearly $3 billion to build a stronger, smarter energy grid, with this powerful of a storm, customers should prepare for potentially prolonged power outages," the company said.

'FPL please'

As Florida residents return home from evacuation centers to survey the damage caused by Irma, some are imploring utility companies to work faster to restore power.

In Islamorada, resident Chris Crooks made a sign for Florida Power & Light company.

"FPL please," the sign simply said, with an arrow pointing to his street. He said he's tried to reach out to the company on social media but his power is still out.

"Maybe somebody can see because I've done all the Facebook stuff and I've done all the apps and this and that ... and they're just 'we're getting to you, we're getting to you," he said.

Several states affected

Massive power outages crippled much of the southeast Tuesday. Among the hardest hit by Irma:

• FLORIDA: About 4.4 million customers are without power across the state, authorities said. They include homes, organizations and businesses.

• GEORGIA: Almost 700,000 customers are in the dark, according to Georgia Power and Georgia EMC.

• SOUTH CAROLINA: Almost 55,000 customers have no power, according to Duke Energy and SCE&G

• NORTH CAROLINA: More than 29,000 customers don't have electricity, according to Duke Energy.

• ALABAMA: More than 7,000 customers are without electricity, Alabama Power said.

Areas cut off

Irma cut off communication in entire neighborhoods. Two days after the storm made landfall on Cudjoe Key, authorities and a few residents were finally able to reach some of the Florida Keys on Tuesday.

What they found was devastating: Based on initial estimates, 25% of the houses on the chain of islands have been destroyed, the Federal Emergency Management Agency said. An additional 65% suffered major damage.

"Basically, every house in the Keys was impacted some way," FEMA Administrator Brock Long said.

But Key West City Manager Jim Scholl told CNN those estimates might be high. The damage in his city and in his neighborhood on Cudjoe Key didn't match those dire numbers, he said.

One of the challenges in Key West is moving debris out of the roadways and fixing the water infrastructure -- the area is under a boil water advisory.

"That's why we don't want people to, en masse, return down here to the Keys. And we certainly understand the frustration," he said. "Everyone wants to get down here and check out their homes."

It's a long wait for those sifting through what's left of their homes throughout Florida in the oppressive heat and high humidity -- doing so while they wait for the power to come back on and thus the air conditioning.

Nine states impacted

Irma, which stretched 650 miles from east to west, has pummeled at least nine states -- deluging city streets, knocking over trees and destroying homes along the way.

At least 17 storm-related deaths have already been reported on the US mainland, according to local officials:

Florida has reported 12 deaths, Alberto C. Moscoso, a spokesman for Florida Division of Emergency Management, said Tuesday evening. 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. South Carolina had two deaths. A 57-year-old man was struck by a falling tree limb during the storm. State emergency officials said a driver with a Florida license plate also died from the storm, but did not give further details.

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 reopened with limited operations Tuesday.

And Florida Hospital, a health provider in the state, said it would reopen many of its impacted facilities on Tuesday or Wednesday.

How to help Hurricane Irma victims

This is the first time 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.