Hurricane Milton is expected to barrel down Mexico’s Yucatán Peninsula, bringing sustained winds of nearly 155 miles per hour as the Category 4 storm heads toward Florida’s dangerously exposed Tampa Bay.

The storm’s track suggested it would pass over the Mexican city of Mérida, home to 1.2 million people, in the early hours of Tuesday morning before turning north towards the US. Mexican officials have transported people from low-lying coastal areas.

Milton is expected to hit Florida’s southwest coast on Wednesday evening local time, the US National Weather Service said in its latest update, and could cause destruction in areas already reeling from the devastation of Hurricane Helene nearly two weeks ago.

Nearly the entire west coast of Florida was under a hurricane warning, with more than a million people ordered to evacuate, fleeing potentially catastrophic damage and power outages that could last days. With one day left for people to leave, local officials expressed concern about traffic jams and long lines at gas stations.

U.S. forecasters and officials fear Milton could make landfall in the Tampa Bay region, home to more than 3 million people. Tampa hasn’t been hit by a major hurricane since 1921, and water levels rose 15 feet.

Hurricane damage modelers have warned for years that the Tampa Bay area is particularly vulnerable to rising sea levels caused by storm surges because of its wide and shallow seafloor, which can push water upward.

Hurricane Helene, which made landfall in late September, caused more than 200 deaths and catastrophic damage stretching from Florida to the Appalachians. There are fears that piles of construction rubble left in Helene’s wake could turn into dangerous rubble if swept away by Milton’s floods and winds.

The National Weather Service downgraded Milton to a Category 4 hurricane early Tuesday, but forecasters said it still posed an extremely serious threat.

“Although fluctuations in intensity are expected, Milton is expected to remain an extremely dangerous hurricane as it makes landfall in Florida,” the agency said.

It will be the tenth major hurricane – Category 3 or higher – to make landfall along the US Gulf Coast since 2017, drawing strength from warm seas in the Gulf. Milton was the third fastest intensifying storm ever recorded in the Atlantic Ocean, the agency said.

Weather and climate experts attribute such a high number of powerful, destructive storms to the climate crisis, fueled by the burning of fossil fuels.

Before Milton arrived, Florida Governor Ron DeSantis declared a state of emergency for 51 of 67 counties. “What you don’t want to do is stay in an area where there’s a 10-foot storm surge,” he told Fox News on Monday.

DeSantis also told Floridians to make sure they had a week’s worth of food and water and to brace for more evacuation orders.

The governor is pro-fossil fuels and has criticized climate action as being led by “radical green fanatics.”

Reuters and Associated Press contributed to this report