And despite being downgraded after moving over Florida and Georgia, it's not over: officials say floodwaters brought by the storm won't peak in some rivers until Tuesday - when new high-water records could be set. Irma is expected to weaken into a tropical storm over far northern Florida or southern Georgia later on Monday but first its centre will continue to move over the western Florida peninsula, the NHC said.
As the hurricane moves north and the wind directions change, the water will start to rush back in and storm surge flooding will occur. That has left more than 6 and a half million homes and businesses across the state without electricity, one of the biggest power outages in the country's history.
Downed trees were a common sight through much of central Florida.
More than four million customers were without power throughout the state, according to Florida's Division of Emergency Management.
The figure represents nearly 60% of the state's electricity users, who were still experiencing power outage as of 9 p.m. EDT Monday, according to the state's Division of Emergency Management.
There are roughly 7 million residential customers in the state.
"Tomorrow we'll assess the damage and try to get the engineering part of it corrected", said Miami's Deputy building Director Maurice Pons. "Basically, every house in the Keys was impacted", FEMA administrator Brock Long said.
WILLIAM PITTMAN: Our lights have been out, went out at about 4:30 this morning, and they're still out.
Anxious relatives, generous volunteers and frantic neighbors turned to social media after Hurricane Irma wiped out electricity and cell service to many communities around Florida, cutting off most contact with remote islands in the Keys.
Every few minutes during the height of the storm, he sent another dispatch. One stretch of the bay was six feet below normal tide.
Boats are seen at a marina in Coconut Grove as Hurricane Irma arrives at south Florida, in Miami, Fla., Sept. 10, 2017.
As Hurricane Irma is now a Tropical Storm when it gets to Jacksonville later this morning.
Elsewhere, Hurricane Katia was also downgraded to a tropical storm after lashing Mexico and leaving two people dead.