At least three people were killed as the strongest Atlantic hurricane to make landfall in more than 80 years hit the southern tip of Florida Sunday, knocking out electricity for more than one million residents.

Hurricane Irma, a Category 5 hurricane, which had been downgraded to a Category 3 as it approached the southeastern United States, regained much of its strength early Sunday morning.

As the hurricane approached the Florida Keys, Irma was upgraded back to a Category 4, Fox News reported.

The hurricane, which killed dozens and caused billions of dollars in damages in the Caribbean before hitting Florida, is now the most strongest Atlantic hurricane to make landfall since 1935.

Residents of southern Florida braced for the hurricane, which made landfall in the Florida Keys by Sunday morning and proceeded northwest of the Miami metropolitan area, through Fort Myers and Naples and towards the Florida panhandle.

On Saturday, Florida Governor Rick Scott warned residents living in Irma’s path to evacuate immediately, noting the storm was likely to ‘re-energize’ and upgrade from a Category 3 to a Category 4.

Meteorologists now say Hurricane Irma will sweep through the western coast of Florida along the Gulf of Mexico, hitting the Tampa Bay area by Sunday night. The storm is expected to continue along the Gulf coast, hitting Tallahassee before cutting across western Georgia and eastern Alabama.