A FEMA search and rescue response team has been deployed from Maxwell Air Force Base in Montgomery, Alabama, to Mexico Beach.
"The worst thing you can do now is act foolishly" by putting yourself in danger or keeping law enforcement from saving lives, he said at a news conference. He advised Gulf Coast residents to prepare for possible evacuation orders and has put more than 5,000 National Guard soldiers on alert.
At least seven people were killed by the storm in Florida, Georgia and North Carolina from falling trees and other hurricane-related incidents, according to state officials.
"We are going to be aggressive with recovery and response over the coming days and will do everything we can to assist our communities that have seen impacts from this devastating storm", he said. As many as 389,639 customers in Florida, 484,487 customers in North Carolina, 117,000 customers in Georgia, 24,000 customers in Alabama, 9,163 customers in SC and 61,067 customers in Virginia.
The Carolinas are still recovering from the floods of Hurricane Florence.
As the storm's fierce winds pushed ocean water onto the Panhandle's Mexico Beach, ABC News' Ginger Zee said she saw an "entire home, a well-built home, rolling down the street".
Home after home was razed from its foundations in the town of around 1,000 people, leaving just bare concrete slabs. The rest were missing roofs or siding. Roads were impassable and canals were choked with debris.
The tropical storm is expected to swell into a Category 1 hurricane as soon as Monday night as it rolls into the U.S. Gulf of Mexico, with winds of 70 miles per hour, forecasters said.
"When the water came in houses started floating", said the man identified as Scott.
When Boutwell returned to his own house, he discovered furniture in his house that wasn't his. The surge had brought stuff in.
The beach town looked like it had been carpet bombed, with little left in the first blocks from the beach. "Our lives are gone here". All the stores, all the restaurants, everything.
"It s hard to grasp", he said.
"This was never in our imagination", he said.
Bobby Smith boarded up windows at Jani's Ceramics in Panama City, Fla.
This time, the Panama City school was ripped apart by Michael.
Margaret Decambre, a 48-year-old gemologist, rode out the storm in her Panama City fourth-floor condo with her husband and three cats. Alabama Gov. Kay Ivey said she fears widespread power outages and other problems would follow.
"We don't know where she's at", he said. That includes grants for temporary housing and home repairs, low-priced loans for uninsured property losses and other programs to help with recovery.
The National Hurricane Center (NHC) described Michael as "potentially catastrophic". However, the storm is still a major concern as it moves through North Carolina and southern Virginia.
There will be no shelters open in Wakulla County, the sheriff's office warned on Facebook, because they are rated safe only for hurricanes with top sustained winds below 178kph.
Long said many Florida buildings were not built to withstand a storm above the strength of a Category 3 hurricane on the five-level Saffir-Simpson Hurricane Wind Scale.
Below are 15 images that personify the aftermath of the Category 4 storm, which blew ashore along the Panhandle packing 155 miles per hour winds.