Florida Governor Rick Scott has declared a state of emergency as Tropical Storm Colin bears down on the state's west coast where it will strike today before crossing into the Atlantic to menace Georgia and South Carolina.

Flood and flash flood warnings stretch from North Carolina to Florida where as much as 13cm of rain will fall across a large area, the US Weather Prediction Centre said. Some areas could get as much as 20cm and evacuations are possible, the National Weather Service said.

The storm is forecast to strike near Florida's Big Bend region, the marshy coast that extends from Indian Pass to Englewood, the National Hurricane Centre in Miami said in an advisory. Gulf of Mexico oil and natural gas platforms off the coasts of Louisiana and Texas are out of the storm's path. Orange juice futures jumped to the highest in more than two years as Colin is expected to reduce the Florida crop.

"Due to the displacement of the strong winds and heavy rainfall from the centre of Colin, it is important to not focus on the exact forecast track," Daniel Brown, a senior hurricane specialist at the hurricane centre in Miami. "Heavy rainfall, strong winds, and coastal flooding will begin affecting portions of the Florida Peninsula well in advance of the centre's nearing the coast."


Scott declared a state of emergency across the central and northern part of the state. Franklin County told residents in low lying areas and in mobile homes they should leave before the storm arrives.

Tropical storm warnings were also issued on the east coast from South Santee River, South Carolina to Sebastian Inlet, Florida. Colin, with top winds of 80 km/h, was 460km west-southwest of Tampa, the hurricane centre said the advisory.

Colin is the third named storm of 2016 and the second in about a week, heralding an early start to the Atlantic hurricane season, which began on June 1. The first storm of the year was Hurricane Alex, which formed in the mid-Atlantic in January. A storm gets a name when its winds reach tropical-storm strength of 62 km/h.

By the time Colin reaches the Atlantic, its winds could peak at 95km/h as it is nudged away from the East Coat by a low pressure system over the eastern part of the country.

While Colin has strengthened some since it first developed on Monday, it is disorganised and facing wind shear, which will probably keep it from getting any stronger, Brown wrote.

"It should be noted that Colin could lose its status as a tropical cyclone while impacts are still occurring along the coast," Brown wrote. "In this case, NHC would anticipate continuing advisories and warnings on the post-tropical cyclone."