Irma made landfall on Marco Island off Florida's west coast with winds of up to 105mph (169km/h) but has since been downgraded from category three to two.
More than 3.4 million homes in the state are without power, and parts of the city of Miami are under water.
Some 6.3 million people in Florida had been told to evacuate.
Three storm-related deaths have been reported, as Irma is moving northwards.
The following are several scenes of devastation in the state.
(Pics : Dailymail)