MIAMI (AFP) - Tropical Storm Andrea, the first of the Atlantic storm season, formed in the Gulf of Mexico on Wednesday and was expected to become a hurricane within 48 hours, the US National Hurricane Center said.

"This system has a high chance - near 100 per cent - of becoming a tropical cyclone during the next 48 hours," the Miami-based NHC warned, with the storm forecast to hit the US state of Florida.

The storm earlier produced driving rains in Cuba's westernmost Pinar del Rio province and led authorities to evacuate more than 1,000 people from low-lying areas.

The Atlantic hurricane season started June 1 and runs through Nov 30.