According to BBC, it has been downgraded from category three to one but still has maximum sustained winds of 85mph (137km/h).
More than 3.4 million homes in the state are without power, with parts of the city of Miami under water.
Three storm-related deaths have been reported and several areas have brought in curfews.
Irma cut a devastating track across 10 Caribbean countries and territories, killing at least 28 people there. BBC reports.
President Donald Trump has approved a major disaster declaration and emergency federal aid for Florida, describing the hurricane as a "big monster".