Trees and branches are seen after being knocked down by the high winds in Miami, Florida. Florida will take a hit by the Hurricane which will come ashore at category 4. Photograph: (AFP)
Hurricane Irma's eyewall slammed into the lower Florida Keys Sunday, lashing the island chain with fearsome wind gusts, the US National Hurricane Center said.
The eye of the Category 4 storm was 15 miles (24 kilometers) southeast of Key West as of 7:00 am local time (1100 GMT), bringing maximum sustained winds of 130 miles per hour and threatening dangerous storm surges.
"This is an extremely dangerous and life-threatening situation!" the National Weather Service in Key West had warned, urging those who had not heeded dire warnings to evacuate to take shelter "now to protect your life!"
The hurricane was moving eight miles per hour northwest, with Florida's west coast cities of Naples, Fort Myers and the densely populated peninsulas of Tampa Bay in its crosshairs.
Irma was upgraded to a Category 4 storm hours earlier as more than six million Floridians had been ordered to evacuate their homes ahead of the monster storm.
For those people still at home, it was too late to escape the wrath of what could be the worst hurricane in storm-prone Florida.
In Key West, police had opened a "shelter of last resort" for those who had ignored mandatory evacuation orders.
"It's going to be horrible," Florida Governor Rick Scott said of Irma on NBC television Sunday morning. "Now we have to hunker down and watch out for each other."
More than 430,000 homes and businesses were without power across the state, mainly in southern Florida, according to utility company Florida Power and Light.
Irma smacked the Keys 57 years to the day that Hurricane Donna hit the same area in 1960, destroying nearly 75 percent of the island chain's buildings.