Florida prepared on Sunday for its largest evacuation since 2017 as Hurricane Milton intensified in the Gulf of Mexico on its path toward the U.S. state's western coast, coming on the heels of the devastating Hurricane Helene.

Milton, which strengthened from a tropical storm to hurricane on Sunday, was projected to make landfall on Wednesday as a major hurricane, likely hitting near the heavily populated Tampa Bay area, the U.S. National Hurricane Center said.

The new hurricane was expected to affect areas already hit hard by Helene, which made landfall further north on Sept. 26.

Kevin Guthrie, director of Florida's emergency management division, urged people to prepare for the "largest evacuation that we have seen most likely since 2017 Hurricane Irma."

Bob Gendron loads sandbags onto his truck, as they are distributed to Pinellas County residents before the expected arrival of Tropical Storm Milton, in Seminole, Florida, U.S. October 6, 2024. REUTERS/Octavio Jones

"I highly encourage you to evacuate," Guthrie told Floridians in a press conference.

Milton was about 780 miles (1,255 km) west-southwest of Tampa as of 7 p.m. EDT on Sunday (0000 GMT on Monday), packing maximum sustained winds of 85 mph (140 km) and moving to the east toward Florida at 7 mph (11 kph), the National Hurricane Center said.

A hurricane watch was in effect for the northern coast of Mexico's Yucatan Peninsula.

The wind speed made it a Category 1 on the five-step Saffir-Simpson scale, though it was likely to be upgraded. The private forecaster AccuWeather expected it would rate a 4 out of 5 on its own scale, capable of widespread catastrophic flooding.

Florida Governor Ron DeSantis warned of a potentially higher storm surge and more power outages from Milton compared to Helene, and said destruction from Helene could be compounded.

"There are some areas with a lot of debris that is there, so if you get hit with a major hurricane, what's going to happen to that debris? It's going to increase the damage dramatically," DeSantis said. "This is all hands on deck to get that debris where it needs to be."

Pinellas County, which includes the city of St. Petersburg, on Monday was likely to issue mandatory evacuations for more than 500,000 people in the lowest lying areas, Sheriff Bob Gualtieri told a press conference.

He urged people to heed evacuation orders after he said too many ignored them for Helene, resulting in 12 deaths in the county and 1,500 emergency calls that were unable to be answered.

The county already ordered the evacuation of six hospitals, 25 nursing homes and 44 assisted living facilities totaling 6,600 patients, said Cathie Perkins, director of the county's emergency management. School was canceled from Monday to Wednesday.

"We already will be rebuilding for years because of Hurricane Helene, and that will be exacerbated by the impacts of this storm," St. Petersburg Mayor Ken Welch said. "Remember, Hurricane Helene was 100 miles (160 km) away from us, moving in a different direction. This is a powerful Cat 2 or Cat 3 hurricane headed directly for us."

North Carolina, Florida and much of the South are still recovering from the massive destruction caused by Helene, which killed more than 200 people across six states, making it the deadliest named storm to hit the mainland U.S. since Hurricane Katrina killed nearly 1,400 people in 2005.

U.S. President Joe Biden said on Sunday he ordered another 500 active-duty troops to move into western North Carolina and assist with the Helene response and recovery efforts, increasing the number to 1,500.

They join a massive state and local recovery effort plus 7,000 people from the federal workforce and 6,100 National Guard personnel, the White House said.

The Biden administration has approved $137 million in federal assistance and promised more aid would be forthcoming, as the economic damage is projected to soar into the billions of dollars.