At least five people have been killed after Hurricane Debby slammed into Florida before weakening to a tropical storm.

Debby is expected to bring heavy flooding to parts of Georgia and the Carolinas in the coming days.

The National Hurricane Center warned of a "life-threatening" flood threat as the "slow-moving storm" drops "torrential rains".

Debby made landfall on Monday morning as a category one hurricane in the Big Bend region of Florida's Gulf Coast.

Authorities said the dead included a 13-year-old boy who was killed when a tree fell onto a mobile home in the town of Levy County, located near Gainesville.

In Hillsborough County – around Tampa - an 18-wheel lorry veered into a canal during the storm. The driver was found dead.

In Dixie County, just west of Gainesville, officials reported that a woman and a 12-year-old were killed when their car crashed on Sunday night.

In southern Georgia, another death - a 19-year-old - was reported after a large tree fell onto a porch at a home in Moultrie, local media reported.

The slow-moving pace of the storm could bring “catastrophic flooding”, Jamie Rhome, the deputy director of the hurricane centre, said.

Debby’s waves and strong winds helped blow 25 packages of cocaine, worth more than $1m, ashore in the Florida Keys, according to the US Border Patrol.

In Florida, some 150,000 homes and businesses were without power on Monday night, according to PowerOutage.com. Another 36,000 residents in Georgia and South Carolina were experiencing outages.

The storm is forecast to skim the coast, drenching south-east Georgia and the Carolinas on Tuesday and Wednesday, before moving inland near the South Carolina coast on Thursday.

Before the storm made landfall, Florida Governor Ron DeSantis declared a state of emergency for 61 of Florida's 67 counties.

Spyridon Aibejeris told USA Today repairs on his Keaton Beach home had just wrapped up two weeks ago from Hurricane Idalia, a category three storm that made landfall last summer.

• Why modern hurricanes are slowing down

“Man, I’ve done this so many times," Mr Aibejeris said.

Forecasters predicted this hurricane season, which runs from 1 June to 30 November, would be a busy one.

The National Oceanic and Atmospheric Administration (Noaa) said there could be up to 25 named storms in 2024.

Between eight and 13 of those storms could develop into hurricanes.

Debby was the fourth named storm of the year.

It is thought that climate change may be making slow-moving hurricanes like this more likely.

As the world heats unevenly, this causes changes in the atmospheric circulations that steer storms across the planet.