National Guard helicopters flew in and out of the mountain hamlet of Jamestown late into Friday night after it became isolated by rushing water that scoured the canyon the village sits in. Rescuers on the ground focused on the town of Lyons, a gateway community to Rocky Mountain National Park.
By Saturday morning, the Guard had evacuated nearly 800 people by air and ground.
More than a dozen helicopters were available to aid with rescue efforts.
"We have the ability to go whenever, wherever," Master Sgt. Cheresa Theiral said.
Still more rain was expected Saturday. And the outlook for anyone who preferred to stay behind was bleak: weeks without power, cellphone service or running water.
"Essentially, what they were threatening us with is, 'If you stay here, you may be here for a month,'" said 79-year-old Dean Hollenbaugh, who was evacuated by helicopter from Jamestown, northwest of Boulder.
For those awaiting an airlift, Guardsmen dropped food, water and other supplies to residents of the winding, narrow canyons that cut through the Rocky Mountain foothills.
As the waters rose, thousands of people fled mountain and downriver towns, where rivers were still swelling and spilling over their banks Saturday.
One was Mary Hemme, 62, who displayed a pair of purple socks as she sat outside the Lifebridge Christian Church in Longmont. They're a memento of the more than 30 hours she spent in an elementary school in the flood-stricken mountain town of Lyons. Many evacuees — eventually rescued by National Guard trucks — got socks because most of them had wet feet, Hemme said.
She recalled the sirens blared at 2:30 a.m. Wednesday.
"Mary we have to go, this place is flooding," she recalled her friend Kristen Vincent saying as they clambered out of a trailer.
Soon the trailer, like others in the park where she was staying, was submerged.