Hurricane Bill is pictured moving through the Atlantic Ocean east of the Lesser Antilles islands of the Caribbean on Monday. (NOAA/Reuters)

The U.S. National Hurricane Centre upgraded a storm churning in the Atlantic Ocean to a hurricane early Monday morning as the first named storm to hit land this year came ashore in Florida.

Hurricane Bill is the first hurricane of the Atlantic season.

Bill was upgraded from a tropical storm at about 5 a.m. AT (4 a.m. ET) on Monday as it churned about 1,735 kilometres east of the Lesser Antilles in the Atlantic.

Bill is moving on a west-northwest track at about 35 km/h with sustained winds of up to 150 km/h and is expected to intensify over the next couple of days, according to the hurricane centre. The hurricane centre said Bill's winds could reach up to 177 km/h.

"Bill could become a major hurricane by Wednesday," the centre said in an alert.

The five-day forecast for Bill shows the hurricane passing northeast of Puerto Rico and heading toward Bermuda.

Earlier Monday, tropical storm Claudette made landfall near Fort Walton Beach, with sustained winds of up to 80 km/h, according to the U.S. National Hurricane Center.

Claudette weakens

Claudette had already dumped heavy rains on the Florida Panhandle on Sunday before hitting land and by mid-morning it had weakened to a tropical depression. All tropical storm warnings were discontinued, said the hurricane centre.

Surf enthusiasts were flocking to beaches in the area on Monday to take advantage of what officials were calling moderate conditions.

"We are going to get some pretty good surf," surf instructor Ben Martin told The Associated Press. "Every surfer that owns a board is going to call in sick."

Continued heavy rains have resulted in flood and flash flood watches being issued for parts of the Florida Panhandle and southern Alabama.

An average of about 100 millimeters of rain is expected in storm-affected regions in the Florida Panhandle, southern Alabama and southwestern Georgia.

The storm is moving northwest at about 19 km/h. It is expected to track over the western portion of the Panhandle before reaching southern Alabama and northeastern Mississippi.

2 storms dissipate

Tropical depression Ana will continue to dissipate as it moves across the Caribbean Sea and reaches the coast of the Dominican Republic by the end of the day, according to the hurricane centre.

Storm watches will remain in effect for Puerto Rico, the U.S. and British Virgin Islands, Antigua, St. Maarten and several other islands in the area for at least 36 hours, according to the hurricane centre.

But several watches, including those in Antigua, Barbuda and Montserrat, have been discontinued.

The forecast indicates the storm could bring up to 100 millimetres of rain to some regions.

In the Pacific, Hurricane Guillermo is continuing to weaken, with winds dropping to 113 km/h.

With files from The Associated Press