The response to some of the worst flooding in Kentucky’s history was entering a pivotal phase on Saturday morning, with the confirmed death toll at 25 and the search for victims poised to accelerate over a battered stretch of central Appalachia.

A cold front is expected to bring clearer weather to flood-stricken areas on Saturday, giving rescue personnel one less obstacle to contend with as they work to pluck more residents off rooftops. Nearly 300 people have been rescued in Kentucky so far, about 100 of them by aircraft, Gov. Andy Beshear told reporters on Friday.

But state officials expect the death toll to keep growing, possibly for weeks, as rescue efforts continue across rugged hills and valleys that remain hard to reach. And with rain in the forecast for Sunday, they feel the urgency to make more progress before water levels have a chance to rise again.

“There’s still a lot of people out there — still a lot of people unaccounted for,” Mr. Beshear said on Friday, as President Biden approved a disaster declaration for the state. “We’re going to do our best to find them all.”

Plenty of challenges remain. One is that some Kentucky communities are either without electricity or cut off from cellphone service. According to poweroutage.us, a website that tracks power interruptions, more than 17,000 households across the state were without power as of 4 a.m. Saturday.

Further flooding is also possible. Some Kentucky creeks and rivers were still rising on Friday, and even as a flood warning in a pocket of eastern Kentucky with more than 46,000 residents expired at 10 p.m., a similar number of residents in that part of the state were under flood warnings or advisories through at least Saturday afternoon. (Linking climate change to a single flood event requires extensive scientific analysis, but the phenomenon is already causing heavier rainfall in many storms. Researchers also expect that, as the climate warms, flash floods will become “flashier”: shorter in timing, greater in magnitude.)