The U.S. National Hurricane Center says Ian has rapidly intensified off Florida’s coast, gaining top winds of 155 mph, just shy of the most devastating Category 5 hurricane status.

Ian is pushing a storm surge that could cause catastrophic damage along the state’s heavily populated Gulf Coast from Bonita Beach to the Tampa Bay region.

“This is going to be a nasty nasty day, two days,” Florida Gov. Ron DeSantis said early Wednesday, stressing that people in Ian’s path along the coast should rush to the safest possible shelter and stay there. “Do what you need to do to stay safe. If you are where that storm is approaching, you’re already in hazardous conditions. It’s going to get a lot worse very quickly. So please hunker down.”

The massive storm appeared on track to slam into the Florida’s southwestern Gulf coast somewhere north of Fort Myers and some 125 miles (201 kilometers) south of Tampa, sparing the bay area from a rare direct hit from a hurricane. The Fort Myers area is popular with retirees and tourists drawn to pristine white sandy beaches and long barrier islands, which forecasters said could be completely inundated.

Forecasters say the stretch from Naples to Sarasota is at highest risk. At least 2.5 million people were ordered to evacuate. Winds and rain have begun intensifying, a day after Ian battered the western tip of Cuba, leaving the entire island without electricity.