TALLAHASSEE, Fla. (AP) -- Tropical Storm Colin was gaining speed and strength Monday on its way to strike Florida, threatening rains forecasters said could cause some serious flooding along much of the state's Gulf coast.

A large portion of Florida's western and Panhandle coast was already under a tropical storm warning when the National Hurricane Center announced that a quickly moving depression had become a named storm. The center said it is the earliest that a third named storm has ever formed in the Atlantic basin.

Colin's maximum sustained winds Monday morning had increased to near 50 mph (85 kph) with some slow strengthening possible during the next two days. The storm was centered about 360 miles (580 kilometers) west-southwest of Tampa and moving north-northeast near 14 mph (22 kph).

Tropical storms carry wind speeds of between 39 mph (63 kph) and 73 mph (117 kph).

"It's going to impact most of the state in some way," Gov. Rick Scott said in a phone interview. "Hopefully we won't have any significant issues here, but we can have some storm surge, some rain, tornados and some flooding."

The center of Colin is expected to approach the coast of the Florida Big Bend area Monday afternoon or evening, forecasters said.

Colin is expected to produce rainfall amounts of 3 to 5 inches and forecasters said up to 8 inches possible across western Florida, eastern Georgia, and coastal areas of the Carolinas through Tuesday.

It is the latest in a series of severe whether events across the country, from record-breaking heat in the West, flooding in Texas and storms that are expected to cause problems in the nation's capital and mid-Atlantic region.