Alamo, Georgia - A tornado killed two people in Georgia, the state's governor said Friday, as Hurricane Helene churned into the state after causing one death in Florida when it barreled ashore in the southeastern US.

Tornado warnings had gone out across northern Florida, Georgia, and the Carolinas before the powerful hurricane made landfall late Thursday.

The US National Hurricane Center warned of "catastrophic winds" and life-threatening storm surge and heavy rains from the hurricane, even as it weakened as it moved inland.

Georgia Governor Brian Kemp said two people died in the city of Alamo, urging "all Georgians to brace for further impact from Helene, remain vigilant, and pray for all those affected" in a post on X.

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Local media had reported a man and a woman died when a trailer was picked up by a tornado, citing Wheeler County Emergency Management Agency Director Steve Adams.

"The trailer was taken across the highway by the tornado, hitting two vehicles, before landing in a field," WTOC-TV news reported.

Earlier in the day, Florida Governor Ron DeSantis said one person had been killed while driving in coastal Tampa city.

"We have had a report of a fatality on the roadway. A car driving on I-40... in Tampa was hit when a sign fell onto the highway," DeSantis said in a briefing on Hurricane Helene.

"It just shows you that it's very dangerous conditions out there," he added. "You need to be right now just hunkering down. Now is not the time to be going out."

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More than 55 million Americans were under some form of weather alert or warning from Hurricane Helene, which officially weakened to a tropical storm early on Friday.

The National Weather Service said the region in the storm's path could be hit extremely hard, with floods not seen in more than a century.

Scientists have been warning for decades that global warming increases the intensity and frequency of extreme weather events.