Maximum sustained winds were at 70 miles (110 km) per hour, the forecaster said.
As early as Sunday morning, about two million homes and businesses were without power - and the Florida Power and Light company issued a warning that thieves were masquerading as utility staff to gain access to homes, which they were robbing. People on the islands of Saint Martin and Saint Barts turn to the colossal task of rebuilding after Hurricane Irma laid waste to their infrastructure and shattered their lives.
"Right now, we're anxious about lives, not cost", Trump said.
The utilities had thousands of workers, some from as far away as California, ready to help restore power once Irma's high winds pass their service areas.
According to the National Hurricane Center's 5 a.m. advisory, Irma was downgraded to a Category 1 storm, still a monster despite the weakening.
Irma is a Category 1 storm, with maximum sustained winds of 70 miles per hour and gusts of more than 90 miles per hour. He praised the federal agencies involved with the storm and said he would go to Florida "very soon".
Irma made landfall as a Category 4 hurricane Sunday morning at Cudjoe Key, not far from Key West. After making landfall on Sunday, the huge storm remained a Category 1 hurricane as it moved over the state's northwest Monday, before finally being downgraded to a tropical storm at 8 a.m. ET.
The National Oceanic and Atmospheric Administration (NOAA) use a measure called Accumulated Cyclone Energy (ACE) to measure the power of hurricanes.
Irma continued its slog north along Florida's western coast having blazed a path of unknown destruction.
Georgia Power spokeswoman Holly Crawford said Monday the areas with the most power outages were Glynn and Chatham counties.More news: US formally requests UN vote on North Korea on Monday
Northeastern Florida cities including Jacksonville were flooding on Monday, with city sheriffs pulling residents from waist-deep water.
- Two tornadoes touched down in Brevard County, destroying mobile homes in their path, officials said. No injuries were reported in either case.
Northern Florida peninsula and southern Georgia: additional 3 to 6 inches with storm total amounts of 8 to 15 inches. FEMA chief Brock Long said some places won't have electricity for weeks.
French aid includes helicopters, engineering equipment, medical supplies and a million litres (265,000 gallons) of water, as the three water-treatment plants will be knocked out for months.
About 2ft (60cm) of water has been seen in Miami's financial district, where one major street resembled a river, but the worst damage is expected on the west coast.
At least 26 people were arrested for burglary and looting Sunday night in Miami, and schools, airports and Orlando's DisneyWorld were on the list of closures.
The storm killed at least 28 people as it raged westward through the Caribbean en route to Florida.
Florida Gov. Rick Scott said Irma's wrath is unprecedented, warning that storm surges could be deadly.
In metro Atlanta, MARTA suspended its Monday bus and rail service ahead of the storm.
This morning, Florida congresswoman Debbie Wasserman Schultz has said that the state will require the most expensive programme in U.S. history to recover. It was one of four hurricanes to hit the Sunshine State that year.