Hurricane Helene live updates: Monster Category 4 storm bears down on Florida

Helene is expected to strengthen to a hurricane on Wednesday as it enters the Gulf of Mexico and strengthen further to a major Category 3 hurricane by Thursday morning.

A hurricane watch is in effect in Florida from Tallahassee to Tampa, where hurricane conditions will be possible late Wednesday night through late Thursday night.

Wednesday night into Thursday morning, Helene’s outer bands will start to lash Florida’s Gulf Coast. The worst of the conditions will be throughout the day on Thursday.

Helene is forecast to make landfall Thursday night along Florida’s Big Bend region as a Category 3 hurricane. Winds could be up to 115 mph during landfall.

Helene is expected to be a large hurricane, which means impacts will extend significantly beyond the center, impacting most of Florida and much of the Southeast.

After landfall, Helene is forecast to quickly move north into Georgia, bringing heavy rain and strong winds to the South.

A significant flash flood risk stretches from the Florida Panhandle to South Carolina -- including Tallahassee to Atlanta -- Thursday night into early Friday.

-ABC News' Melissa Griffin

Ten to 15 feet of dangerous storm surge is forecast for Florida’s Big Bend area. Tampa Bay could see 4 to 8 feet of storm surge.

Four to 8 inches of rain is expected from Helene, with 12 inches locally, bringing major flash flooding.

Tornadoes are also possible on Wednesday and Thursday.

Damaging wind gusts over 100 mph will be possible in Tallahassee and Florida’s Big Bend area during landfall Thursday night.

-ABC News' Melissa Griffin

Ahead of Helene, Florida A&M University in Tallahassee canceled class from Tuesday afternoon through Friday. The university will be closed Wednesday through Friday.

Florida A&M said this weekend’s home football game and parents’ weekend will be rescheduled.

Florida State University said its Tallahassee campus will be closed from Wednesday morning to Sunday night.

FSU Tallahassee students can stay on campus during the closure, but should plan for possible power outages and be prepared to possibly stay inside all day Thursday, the university warned.

Officials in Florida are also closing public schools in multiple counties, including Pasco, Pinellas, Hernando, Citrus and Sarasota.

Mandatory evacuations have been announced in parts of Charlotte and Franklin counties.

Helene, currently located about 180 miles east southeast of Cozumel, Mexico, strengthened to a tropical storm on Tuesday morning.

The forecast shows Helene moving through the Yucatan Channel Wednesday morning, bringing near hurricane-force wind gusts to Cancun, Mexico.

By Thursday morning, coastal flooding will reach Florida, including Naples and Fort Myers.

On Thursday night, Helene will make landfall near Apalachicola, Florida.

Dangerous wind gusts up to 105 mph are expected and storm surge will be a major threat for the Tampa Bay area.

By Friday morning, the center of Helene will be near Atlanta, bringing strong winds to Georgia, Tennessee, South Carolina and North Carolina.

Downed trees and power lines will be a major danger across the Southeast.

The flash flood threat will continue into the weekend in the Tennessee, Ohio and Mississippi River Valleys.