The warning means that hurricane conditions could develop in the area over the next 24 hours. Tropical storm Alberto, the first named storm of the season, is expected to bring heavy rainfall to Florida.
The storm would become a hurricane if it has sustained winds of 120 kilometres per hour. Alberto on Monday had winds of more than 100 kilometres per hour.
Florida Governor Jeb Bush on Monday declared a state of emergency in anticipation of the storm hitting.
Alberto, the first storm since the beginning of the hurricane season just 10 days ago, is expected to make landfall on the Florida coast Tuesday.
In 2006, a series of hurricanes wreaked havoc in many areas of the US and Central America. About 1,300 people died when hurricane Katrina hit the US Gulf Coast in August, flooding almost the entire city of New Orleans and causing billions of dollars worth of damage.
The US' National Hurricane Centre in May predicted a 'very active,' above-average Atlantic hurricane season this year. Between four to six major hurricanes were predicted to hit the Atlantic area.
