Sand bags were being distributed to residents in St. Petersburg, Tampa and nearby cities.
Hurricane officials say a storm in the northwestern Caribbean Sea could develop into a tropical storm before hitting Florida with flooding rain.
The National Hurricane Center said a hurricane hunter plane will investigate the storm near Mexico's Yucatan Peninsula Sunday afternoon. It already contained thunderstorms and near tropical storm strength winds.
There is a 90 per cent chance the weather system could develop into a tropical depression or named storm by Sunday night or Monday morning.
Regardless of development, heavy rains and flooding are expected in the Yucatan Peninsula, western Cuba, the Florida Keys and Florida's Gulf Coast over the next few days.
Florida Gov. Rick Scott planned a briefing with state emergency management officials Sunday afternoon.
Sand bags were being distributed to residents in St. Petersburg, Tampa and nearby cities.
TAKING AIM AT THE NATION'S CAPITALMore than 17 million people in Washington, D.C., Baltimore, Virginia Beach, Virginia, and Raleigh, North Carolina, are looking at an "enhanced" risk of severe thunderstorms Sunday, according to the National Weather Service's Storm Prediction Center.
Damaging winds, a tornado or two and marginally severe hail are expected as far north as New York.
BRUSHFIRES AND WILDFIRESFirefighters are spending the weekend battling blazes in California, New Mexico and Arizona.
A wildfire sparked by lightning burned nearly 12 square miles in the San Mateo Mountains near Magdalena, which is about 100 miles southwest of Albuquerque, New Mexico.
In Arizona, firefighters are fighting a much larger blaze. The Juniper Fire just south of the town of Young is now burning on over 28 square miles in the Tonto National Forest. It too was caused by lightning.
Officials say the extreme heat and a dry winter mean there's a high risk of wildfires. Summer has typically been considered wildfire season but experts now say blazes happen year-round.
In Southern California, a brush fire burned 30 acres near Temecula, forcing the closure of the southbound I-15 freeway. No homes were immediately threatened.