But Irma again intensified over the warm waters approaching the Florida mainland, making it a Category 4, then shortly thereafter a 3 (still considered a major hurricane). Incredibly, Irma was a hurricane for 11.25 days, which is the most since Ivan in 2004.
The storm made a second landfall hours later as a Category 3 storm on Marco Island, a city and barrier island off Florida's southwest coast, before weakening again.
Irma hit southwest Florida on Sunday morning as a risky Category 4 storm, the second-highest level on the five-step Saffir-Simpson scale. That toll included 10 killed in Cuba and state media said most of those died in Havana, where seawater surged deep into residential neighborhoods.
The National Oceanic and Atmospheric Administration (NOAA) use a measure called Accumulated Cyclone Energy (ACE) to measure the power of hurricanes.
The string of islands was the first part of the state hit by the storm, and were still without water, power or cell service Monday.
Florida Governor Rick Scott expressed his condolences to the families of the deceased.
Florida Highway Patrol tweeted that "Now is NOT the time to go sightseeting" in Jacksonville, and that risky conditions still persist throughout the city.
"Wherever Hurricane Irma goes, we'll be there first", Pence said. It battered Florida's lower half, leaving a trail of tornadoes and storm-surge flooding as its core slowly moved inland. There were no immediate reports of deaths in Florida.
Strom surge warnings are in place for areas including Tampa Bay as well as many areas in South Florida.
Irma did not cause as much damage in Florida as some forecasters had feared.
Irma made landfall just after 9am at Cudjoe Key, about 20 miles outside Key West. John Ward, the emergency operations manager of Clay County, says crews have pulled 46 people from flooded homes by early Monday and an undetermined number are still stranded as the area's creeks and ponds are getting record flooding. Florida is the worst-affected state, with 5.7 million customers now without electricity, according to FloridaDisaster.org. "It is because of their work we are able to live in a state where people can raise their families safely", he said in a statement.
"I've been here with other storms, other hurricanes". At least 6.5 million residents of Florida have been asked to evacuate while many residents continue to seek shelter in safer areas.
As of 10 a.m. Tuesday the center of Post-Tropical Storm Irma was located about 50 miles north-northwest of Birmingham and was moving to the north-northwest at 26 mph, according to NOAA's Weather Prediction Center.