Torrential rains unleashed devastating floods in Appalachia on Thursday, as fast-rising water killed at least eight people in Kentucky and sent people to their rooftops to be rescued.

Water gushed from hillsides and flooded out of streambeds, inundating homes, businesses and roads throughout eastern Kentucky. Parts of western Virginia and southern West Virginia also saw extensive flooding. Rescue crews used helicopters and boats to pick up people trapped by floodwaters.

Kentucky Gov. Andy Beshear tweeted Thursday evening that the state's death toll from flooding had risen to eight. He asked for continued prayers for the region, which was bracing for more rain.

"In a word, this event is devastating," Beshear said earlier in the day. "And I do believe it will end up being one of the most significant, deadly floods that we have had in Kentucky in at least a very long time."

In Breathitt County in Kentucky, Krystal Holbrook's family raced against surging floodwaters in the early morning hours to move possessions to higher ground. Their ordeal began around 4 a.m. Thursday, as they scurried in the dark to move vehicles, campers, trailers and farm equipment. But as the water kept rising throughout the day, the concern was that "higher ground is getting a little bit difficult," she said.

"It looks like a huge lake back here," she said.

Beshear warned that property damage in Kentucky would be widespread. The governor said officials were setting up a site for donations that would go to residents affected by the flooding.

Dangerous conditions and continued rainfall hampered rescue efforts Thursday, the governor said.

"We've got a lot of people that need help that we can't get to at the moment," Beshear said. "We will."

Flash flooding and mudslides were reported across the mountainous region of eastern Kentucky, western Virginia and southern West Virginia, where thunderstorms dumped several centimeters of rain over the past few days.

With more rain expected in the area, the National Weather Service said additional flooding was possible into Friday in much of West Virginia, eastern Kentucky and southwest Virginia. Forecasters said the highest threat of flash flooding was expected to shift farther east into West Virginia.

Poweroutage.us reported more than 31,000 customers without electricity in eastern Kentucky, West Virginia and Virginia, with the bulk of the outages in Kentucky.

"There are a lot of people in eastern Kentucky on top of roofs waiting to be rescued," Beshear said earlier Thursday. "There are a number of people that are unaccounted for and I'm nearly certain this is a situation where we are going to lose some of them."

Rescue crews worked throughout the night helping people stranded by the rising waters in eastern Kentucky's Perry County, where Emergency Management Director Jerry Stacy called it a "catastrophic event."

"We're just in the rescue mode right now," Stacy said, speaking with The Associated Press by phone as he struggled to reach his office in Hazard. "Extreme flash flooding and mudslides are just everywhere."

Roads in many areas weren't passable after as much as 15 centimeters of rain had fallen in some areas by Thursday, and 7.5 centimeters more could fall, the National Weather Service said.

Beshear said he has deployed National Guard soldiers to the hardest-hit areas, and three parks in the region were opened as shelters for displaced people.

Gov. Jim Justice declared a state of emergency for six counties in West Virginia after severe thunderstorms this week caused significant local flooding, downed trees, power outages and blocked roads.

Communities in southwest Virginia also were flooding, and the National Weather Service office in Blacksburg, Virginia, warned of more showers and storms Thursday.