Miami, Sep 10: Florida residents were asked to stop evacuating and start seeking shelter as violent winds and rains from hurricane Irma has begun pounding the southern tip of the US state, the media reported. Irma's powerful winds of of 74 mph and outer rain bands lashed the Florida Keys late Saturday night as the massive storm slowly began turning from Cuba's northern coast up into the Florida Strait, CNN quoted the National Hurricane Centre (NHC) as saying. With maximum sustained winds of 120 mph, Irma is expected to strengthen once it moves away from Cuba, with the possibility of hitting the US mainland as a Category 4 hurricane. Irma's eye is expected to cross the lower Florida Keys on Sunday morning before driving up the state's west coast in the afternoon, according to the NHC. So far, at least 36 million people were under hurricane warning Saturday night, CNN reported. As Irma drew closer to the third most populous US state, officials warned the 6.5 million Floridians under mandatory evacuation orders that they were down to their last hours to make a decision. "If you have been ordered to evacuate, you need to leave now. This is your last chance to make a good decision," Florida Governor Rick Scott said at a news briefing on Saturday evening. Federal Emergency Management Agency Administrator Brock Long told CNN: "If you didn't evacuate the Keys, you're on your own until we can actually get in there and it's safe. "The message has been clear: The Keys are going to be impacted. There is no safe area within the Keys. And you put your life in your own hands by not evacuating." Since Irma made landfall early Wednesday morning in the Caribbean, at 24 people have been killed so far and has left entire islands in ruins. The major concern for Florida was the storm surge, which is like a sustained high tide that can cause devastating flooding, warning that it could reach as high as 15 feet in some areas. A storm surge warning is in place for the Florida Keys, Tampa Bay, and an extensive stretch of coastline wrapping most of the way around the state. At 11 p.m. on Saturday night, it was extended as far west as the Ochlockonee River. "You can't survive these storm surges...You've got to get out. You've got to evacuate. This storm is coming. Once the storm's here, we can't evacuate anybody," Governor Scott told CNN. After lashing the Caribbean islands and Puerto Rico, Irma hit Cuba's Ciego de Avila province late Friday night as a Category 5 hurricane before it weakened. Waves as high as 23 feet were recorded, according to Cuban authorities.