"It's appalling. The number of Kentucky people we've lost now stands at 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 the emergency services, including the national guard, the 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, associated with other factors linked in particular to land development, promote flooding.
