New York, Aug 30 (IANS): Tropical Storm Idalia has strengthened to a Category 2 hurricane as it was heading toward the Gulf Coast in the US state of Florida, forcing an emergency declaration, mass evacuations and flight cancellations as it is expected to make landfall Wednesday morning.

The hurricane was forecast to develop into an "extremely dangerous major hurricane" and lash the Gulf Coast, Xinhua news agency reported, citing the US National Hurricane Center.

It could intensify at least to a Category 3 hurricane - classified as a major hurricane, bringing powerful winds and a potential storm surge of 10 to 15 feet.

Idalia put most of Florida's 21 million residents, along with those in the southern parts of Georgia and South Carolina, under hurricane, tropical storm and storm surge warnings and advisories.

Florida Governor Ron DeSantis on Monday declared a state of emergency in 46 counties, a broad swath that stretches across the northern half of the state from the Gulf Coast to the Atlantic Coast. The number was expanded to 49 counties on Tuesday.

"Buckle up for this one," DeSantis, who suspended his presidential campaign due to the crisis, said at a news conference on Monday afternoon, urging Floridians to prepare for potentially dangerous conditions.

According to local officials, more than 5,500 National Guard members have been mobilized and over 580 rescue personnel have been stationed for storm response.

Evacuation notices have been issued in at least 22 counties in the state. Many of the notices were for people in low-lying and coastal areas.

Hundreds of flights have been cancelled as two of the region's largest airports - Tampa International Airport and St. Pete-Clearwater International Airport - suspended commercial operations on Tuesday. Amtrak has cancelled at least 12 East Coast routes and is modifying others.

At least 42 school districts have announced closures over the next two days, along with 16 state colleges and seven universities.