PANAMA CITY — The third-most powerful hurricane to hit the U.S. mainland in recorded history left a wide path of destruction, destroying homes and shopping centers and felling trees that killed at least two people in Florida and Georgia. And it’s not done yet.

Hurricane Michael finally weakened to a tropical storm on Thursday, no longer a Category 4 monster packing 155 mph winds. But it was still menacing the Southeast with heavy rains, blustery winds and possible spinoff tornadoes, soaking areas swamped by epic flooding last month from Hurricane Florence.

By 5 a.m., Michael’s eye was about 45 miles west of Augusta, Georgia, packing top winds of 50 mph and moving at 21 mph into South Carolina, the National Hurricane Center in Miami said.

Thousands of law enforcement officers and search and rescue teams rolled out in its wake to find survivors amid the wreckage of homes where people defied evacuation orders. Michael washed away white sand beaches, hammered military bases and destroyed coastal communities, stripping trees to stalks, shredding roofs, toppling trucks and pushing boats into buildings.

Many homes were ripped apart or washed away altogether in Mexico Beach, a town of 1,000 where the hurricane made landfall and the storm surge pushed lead-grey water up to the rooftops. Authorities said falling trees killed a man outside Tallahassee, Florida, and an 11-year-old girl in southwest Georgia.

It will take some time for residents of north Florida to take stock of the enormity of the disaster. Reaching the worst-hit areas wasn’t easy: Authorities closed Interstate 10, the main east-west route along Florida’s Panhandle, for 80 miles to clear debris, the Florida Highway Patrol said.

Damage in Panama City, just west of where Michael came ashore Wednesday afternoon, was so extensive that broken and uprooted trees and downed power lines lay nearly everywhere. Roofs were peeled away, sent airborne, and homes were split open by fallen trees. Twisted street signs lay on the ground. Palm trees whipped wildly in the winds. More than 380,000 homes and businesses were without power at the height of the storm.

Vance Beu, 29, was staying with his mother at her home, Spring Gate Apartments, a complex of single-story wood frame buildings where they piled up mattresses around themselves for protection. A pine tree punched a hole in their roof and his ears even popped when the barometric pressure went lower. The roar of the winds, he said, sounded like a jet engine.

“It was terrifying, honestly. There was a lot of noise. We thought the windows were going to break at any time,” Beu said.

Sally Crown rode out Michael on the Florida Panhandle thinking at first that the worst damage was the many trees downed in her yard. But after the storm passed, she emerged to check on the cafe she manages and discovered a scene of breathtaking destruction.

“It’s absolutely horrendous. Catastrophic,” Crown said. “There’s flooding. Boats on the highway. A house on the highway. Houses that have been there forever are just shattered.”

A Panhandle man was killed by a tree that toppled on a home, Gadsden County Sheriff’s Office spokeswoman Anglie Hightower said. But she added emergency crews trying to reach the home were hampered by downed trees and debris blocking roadways. The debris was a problem in many coastal communities and still hundreds of thousands of people were also left without power.

Gov. Rick Scott said search and rescue efforts would be “aggressive.”

“Hurricane Michael cannot break Florida,” Scott vowed.

Michael sprang quickly from a weekend tropical depression, going from a Category 2 on Tuesday to a Category 4 by the time it came ashore. More than 375,000 people up and down the Gulf Coast were ordered or urged to evacuate, but it moved so fast that people didn’t have much time to prepare, and emergency authorities lamented that many ignored the warnings , thinking they could ride it out.

In Panama City, plywood and metal flew off the front of a Holiday Inn Express. Part of the awning fell and shattered the glass front door of the hotel, and the rest of the awning wound up on vehicles parked below it.

“Oh my God, what are we seeing?” said evacuee Rachel Franklin, her mouth hanging open.

Based on its internal barometric pressure, Michael was the third most powerful hurricane to hit the U.S. mainland, behind the unnamed Labor Day storm of 1935 and Camille in 1969. Based on wind speed, it was the fourth-strongest, behind the Labor Day storm (184 mph), Camille and Andrew in 1992.

The storm is likely to fire up the debate over global warming. Scientists say global warming is responsible for more intense and more frequent extreme weather, such as storms, droughts, floods and fires, and Michael was fueled by abnormal water temperatures in the Gulf — 4-to-5 degrees above the historic norm for this time of year. But without extensive study, they cannot directly link a single weather event to the changing climate.

After Michael left the Panhandle late Wednesday, Kaylee O’Brien was crying as she sorted through the remains of the apartment she shared with three roommates at Whispering Pines apartments, where the smell of broken pine trees was thick in the air. Four pine trees had crashed through the roof of her apartment, nearly hitting two people.

Her biggest worry: finding her missing 1-year-old Siamese cat, Molly.

“We haven’t seen her since the tree hit the den. She’s my baby,” a distraught O’Brien said, her face wet with tears.