After what she called a terrifying night bunkered in her house in St. Petersburg, on Florida's Gulf Coast, with her children and extended family, Julie Hally emerged with relief on Monday. The winds had toppled some large tree branches and part of a fence, but her house was undamaged.
"My heart just pounded out of my chest the whole time," said Hally, 37. "You hear stuff hitting your roof. It honestly sounds like somebody is just whistling at your window the whole night. Its really scary."
Governor Rick Scott said he would travel later on Monday to the Florida Keys. Irma first came ashore at Cudjoe Key as a Category 4 hurricane with sustained winds of up to 130 mph.
President Donald Trump in a ceremony at the Pentagon to remember the victims of the Sept. 11, 2001, attacks vowed a full response to Irma, as well as continued federal support for victims of Hurricane Harvey, which flooded Texas.
"These are storms of catastrophic severity and we are marshaling the full resources of the federal government to help our fellow Americans," Trump said. "When Americans are in need, Americans pull together and we are one country."
The state's largest city, Miami, was spared the brunt of the storm but still saw heavy flooding. Utility crews were already on the streets there clearing downed trees and utility lines. All causeways leading to Miami Beach were closed by police.
As it traveled through the center of the state early on Monday, Irma brought gusts of up to 100 mph and torrential rain to areas around Orlando, one of the most popular areas for tourism in Florida because of its cluster of theme parks, the National Weather Service said.
A piece of a McDonald's "golden arch" sign hung in a tree near the fast-food restaurant in the central Florida city of Kissimmee on Monday morning. Valerie Gilleece, 55, had ridden out the storm in the city because her wheelchair-bound husband insisted on it, she said.
"I'm just thanking God to be alive," Gilleece said. "I wanted to go from the start but he's stubborn as hell."
Over the weekend, Irma claimed its first U.S. fatality - a man found dead in a pickup truck that had crashed into a tree in high winds in the town of Marathon, in the Florida Keys, local officials said.
During its passage through the Caribbean en route to Florida, Irma was ranked at the rare top end of the scale of hurricane intensity, a Category 5, for days. It carried maximum sustained winds of up to 185 mph when it crashed into the island of Barbuda on Wednesday.
Ahead of Irma's arrival, some 6.5 million people in southern Florida, about a third of the state's population, were ordered to evacuate their homes. Some 200,000 were housed in shelters during the storm, according to federal officials.
Delta said it has decided to cancel about 800 flights Monday as Irma tracks toward its Atlanta hub with "strong crosswinds that exceed operating limits on select mainline and regional aircraft." Over the weekend, Irma grounded a greater-than-expected 12,000-plus flights on four continents.
Miami and Tampa international airports, as well as airports in Fort Lauderdale, West Palm Beach, were closed on Monday.