The death toll from the devastating floods in Kentucky has risen to 15 and is expected to double again, the governor of this US state said on Friday.

“It is appalling. The number of Kentucky residents we have lost is now 15, and is expected to at least double again,” Andy Beshear told CNN television.

The toll, which was previously eight dead, "will also include children," added the elected Democrat.

All emergency services, including the National Guard, police and reinforcements from neighboring states, are mobilized to help the victims of the "worst floods ever experienced by Kentucky", he said.

Torrential rains fell on the east of this rural state overnight from Wednesday to Thursday, turning some roads into rivers and forcing residents to take refuge on the roof of their houses while waiting for help.

About 50 air rescues and hundreds of boat rescues have already taken place, according to Beshear.

“But there is so much water, the currents are so strong that we cannot reach everyone,” added the elected Democrat, who hopes to see the federal government pronounce a declaration of natural disaster during the day. .

Precipitation is expected to continue through Friday evening, and the flood alert has been maintained.

With human-induced global warming, the atmosphere contains more water vapour, increasing the chances of heavy rainfall events, scientists say. These rains, combined with other factors related in particular to land use planning, favor flooding.