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By Tim Stelloh and Alex Johnson

A tropical depression churning toward Florida strengthened into Tropical Storm Colin and was headed toward a wide area spanning the Gulf of Mexico to the Atlantic Seaboard, the National Weather Service said Monday morning.

At 1 a.m. ET, Colin was about 455 miles southwest of Tampa Bay, packing maximum sustained winds of 40 mph and barreling north at 12 mph.

A forecast map early Monday by the National Weather Service shows the predicted five-day track Tropical Storm Colin.National Weather Service

A tropical storm watch for Florida and the Carolinas coast was expanded to cover the entire Gulf of Mexico and the southeast Atlantic Coast on Sunday night. A tropical storm warning was later put into effect from Altamaha Sound, Georgia, to Sebastian Inlet, Florida.

As much as 8 inches of rain is forecast all the way from Mexico's northeast Yucatan peninsula south to western Cuba and north to western Florida, eastern Georgia and coastal areas of the Carolinas after the storm makes landfall late Monday or early Tuesday.

Danielle Banks, a meteorologist for The Weather Channel, predicted tropical-force winds and storms across, but she said Sunday that coastal flooding and storm surge could be a particular problem for Florida.

After a briefing on the storm, Gov. Rick Scott said on Twitter that "every FL family & visitor needs to prepare now" for Colin and develop an emergency plan.

Related: NOAA Predicts Near-Normal 2016 Atlantic Hurricane Season

With the possibility of 12-foot waves, the Coast Guard urged boaters to stay out of the water until Tuesday, NBC Miami reported, and authorities were distributing sandbags to residents in St. Petersburg and Tampa Bay, according to NBC station WBBH of Fort Myers.

Although the 2016 Atlantic hurricane season began five days ago, Colin is the third storm of the year. Hurricane Alex, which slammed the Azores, became the second storm on record to form in January.

Last week, Tropical Storm Bonnie brought heavy rain to parts of the Carolinas and Georgia.