Updated August 28, 2023 at 5:18 AM ET

A tropical storm churning in the Gulf of Mexico could reach hurricane strength and is expected to begin moving north toward Florida and the southeastern U.S. in the coming days.

Forecasters say the system, known as Tropical Storm Idalia, could intensify in the warm Gulf of Mexico waters and has the potential to clobber western Florida and the Panhandle with severe weather starting on Tuesday.

"If you're anywhere along the western Florida peninsula — so let's say from about Fort Myers northward to the Panhandle — you really got to be paying attention, even if you're outside of the cone," National Hurricane Center deputy director Jamie Rhome said in a video briefing Sunday morning.

At about 5 a.m. ET on Monday, Idalia was stationary about 125 miles off the western tip of Cuba, with its highest sustained winds at 65 mph, the NHC said. A hurricane watch was in effect for a wide swath of Florida's west coast, from Englewood to Indian Pass, including Tampa Bay.

Florida Gov. Ron DeSantis has declared a state of emergency for 33 counties and authorities there have begun preparing storm response resources, such as high-water vehicles and boats.

Florida's Division of Emergency Management is encouraging residents with vehicles to keep their gas tanks at least half-full in case officials order any evacuations.

If Idalia becomes a hurricane when its sustained winds reach more than 75 mph and comes ashore in the U.S. at that strength, it would be the first Atlantic hurricane to strike the U.S. this year.

But it's still unclear exactly how strong Idalia will grow and what path it will take.

Tropical storm warnings were in effect Sunday for parts of Mexico and western Cuba with the potential for heavy rain, flash flooding and landslides.

In the coming days, Idalia is expected to move north through the Gulf of Mexico, where forecasters say it could gather strength and turn into a hurricane.

"There's a notable risk of rapid intensification while the system moves across the record warm eastern and northeastern Gulf of Mexico," the National Hurricane Center said in a Sunday morning forecast.

Idalia could begin to have an impact on parts of Florida as early as Tuesday morning.

Rhome noted that the Florida Panhandle is particularly vulnerable to storm surge and that that was also a concern with Idalia. "It will not take a strong system or a direct hit to produce significant storm surge," he said.

He added that other states in the southeastern U.S. such as Georgia and the Carolinas can expect to see heavy rainfall midweek and later regardless of how strong Idalia becomes.

A separate hurricane, Franklin, was active in the western Atlantic Ocean on Sunday. Franklin was expected to impact parts of Bermuda but not make a direct hit on the continental U.S., though Rhome noted that the storm could produce rip currents on beaches along the East Coast.

Copyright 2023 NPR. To see more, visit https://www.npr.org.