Florida declared a state of emergency on Monday as Tropical Storm Debby barreled in from the Gulf of Mexico with torrential rain and strong winds causing power outages and flash flooding.

At least on woman died in a tornado that local media attributed to Debby and state authorities warned that more deadly twisters were possible.

Florida Governor Rick Scott issued a statement declaring a state of emergency, which allows disaster funds to be unlocked and evacuation plans to be enacted.

"Tropical Storm Debby poses a severe threat to the state of Florida and requires that timely precautions be taken to protect the communities, critical infrastructure, and general welfare of this state," it said.

The slow-moving storm, forecast to make landfall on Wednesday somewhere on the Florida Panhandle, the northwestern part of the state bordering Alabama, has already knocked out power to some 35,000 Floridians.

As of Monday evening it was packing sustained winds of up to 45 miles per hour (75 kilometers per hour), with stronger gusts.

"Tropical storm force winds, heavy rainfall and isolated tornadoes are the main concerns today," said a statement from the Florida Division of Emergency Management.

"Rainfall amounts of 5+ inches today and tonight may lead to continued flooding for many areas of the state. In addition, locally heavy rainfall of potentially up to 10-20 inches through the next few days will continue to exacerbate flooding concerns of some areas."