Story highlights More than 17,000 residential structures have been damaged; some 1,500 destroyed

"It's funny the things you think are important," says one evacuee

Another person is presumed dead, which could bring the overall death toll to six

"Mother Nature is not cooperating."

That was the message Sunday from frustrated authorities battling even more bad weather in flood-hit Colorado.

Heavy clouds and rain grounded helicopters, slowing the search for the nearly 500 people who remain unaccounted for. Authorities fear as many as six may be dead.

"Mother Nature is not cooperating with us today, and currently we are not flying. But tomorrow if we get that window of opportunity, which is sounds like we might get, we have the horsepower to hit it hard," incident commander Shane Del Grosso told reporters.

Up to 1,000 people are waiting to be evacuated, he said.

In the meantime, authorities are looking for opportunities to get in by ground and planning their next steps.

But they are waiting for their break.

"We need a change in the weather pattern ... to really go after what needs to be done out there," Del Grosso said.

'A river outside our door'

Photos: National Guard evacuates flood victims Photos: National Guard evacuates flood victims National Guard helps with Colorado evacuations – Members of the Colorado National Guard help Boulder County authorities evacuate residents of Lyons, Colorado, to Longmont, Colorado, on Friday, September 13. Flooding has hit the area hard, washing out roads, damaging bridges and destroying homes. Hide Caption 1 of 13 Photos: National Guard evacuates flood victims National Guard helps with Colorado evacuations – The guardsmen are using Light Medium Tactical Vehicles, or LMTVs, which can transport about 16 people with luggage, to assist the evacuation. The LMTVs can navigate through rubble and flooded areas that otherwise could not be reached by rescue personnel. Hide Caption 2 of 13 Photos: National Guard evacuates flood victims National Guard helps with Colorado evacuations – Dick and LaRue Vodime, temporary residents of Lyons, witness some of the destruction from the floods as they are evacuated to Longmont on September 13. Hide Caption 3 of 13 Photos: National Guard evacuates flood victims National Guard helps with Colorado evacuations – Colorado Army National Guard Sgt. David Wilson carries Ezra Villa while escorting Thomas Walter and Melinda Villa to the flood evacuation area in Lyons on September 13. Hide Caption 4 of 13 Photos: National Guard evacuates flood victims National Guard helps with Colorado evacuations – Residents ride in the back of an LMTV while being evacuated to Longmont on September 13. Hide Caption 5 of 13 Photos: National Guard evacuates flood victims National Guard helps with Colorado evacuations – A Colorado Army National Guard helicopter takes off from the the Boulder Municipal Airport in Boulder, Colorado, on September 13. Hide Caption 6 of 13 Photos: National Guard evacuates flood victims National Guard helps with Colorado evacuations – Guardsmen help residents and their pets off a Colorado National Guard Chinook helicopter at the Boulder Municipal Airport on September 13. Hide Caption 7 of 13 Photos: National Guard evacuates flood victims National Guard helps with Colorado evacuations – Colorado National Guardsmen assist residents in unincorporated areas of Boulder County, Colorado. Residents were evacuating the area on Thursday, September 12. Hide Caption 8 of 13 Photos: National Guard evacuates flood victims National Guard helps with Colorado evacuations – The guardsmen brought in high-clearance vehicles to take people out of the flooded areas. Hide Caption 9 of 13 Photos: National Guard evacuates flood victims National Guard helps with Colorado evacuations – People, as well as pets, were loaded onto National Guard vehicles. Hide Caption 10 of 13 Photos: National Guard evacuates flood victims National Guard helps with Colorado evacuations – The rains sent virtually every waterway in Boulder County coursing out of its banks, and massive water flows washed away roads and bridges, flooded homes and stressed numerous other bridges. Hide Caption 11 of 13 Photos: National Guard evacuates flood victims National Guard helps with Colorado evacuations – Authorities reported between 25 and 30 roads were closed as of Thursday afternoon in Boulder County. Some of them had been washed out entirely. Hide Caption 12 of 13 Photos: National Guard evacuates flood victims National Guard helps with Colorado evacuations – Friday's forecast calls for three more days of rain for the area. Hide Caption 13 of 13

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All things considered, Tim Ferenc and Kerry Cerelli consider themselves lucky.

The Boulder couple woke up early one morning last week to a rushing river.

"We heard what sounded like strong wind or a river outside our door," she said. Video he shot showed water running right around their house.

In case they couldn't later, they decided to evacuate.

"It's funny the things you think are important. In that moment, it was our dog, I grabbed my birth certificate, and a couple of our stuffed animals from our childhood, and that was the only thing that seemed important at the moment -- just us and a couple of sweet things," said Cerelli.

The outside of their home is a mess, but the structure itself is in pretty good shape, Ferenc said.

Others weren't so lucky.

According to the Colorado Office of Emergency Management, the floods have destroyed 1,502 residential structures and damaged 17,494.

They have also been blamed for as many as six deaths, counting two people presumed to have been killed.

The four confirmed deaths include a man and a woman, both 19, who were swept away after leaving their car Thursday in Boulder County. Authorities said the woman left the car first, and the man jumped out to try to save her.

Another body was found in a collapsed home in Jamestown in the same county. Rescuers recovered a fourth body on a roadway in Colorado Springs in El Paso County.

Those presumed dead include a 60-year-old woman and an 80-year-old woman, both in Larimer County.

Witnesses saw the younger woman swept away by floodwater that demolished her house. The older woman suffered injuries and was unable to leave her home.

An additional 482 people remained unaccounted for in Larimer County and 318 in Boulder County. Authorities believe most or all of those people are safe but simply out of touch with relatives or officers who found their homes empty.

"They are taking this stuff back'

Despite the devastation, Larimer County Sheriff Justin Smith told reporters Sunday that some of what he's seen has restored his hope.

The roads and homes might be gone, he said, but "inch by inch, mile by mile, community by community, they are taking this stuff back."

Smith spoke of firefighters who pulled signs out of the mud and residents using their ATVs to rescue neighbors.

He recalled "hearty people" who didn't wait for officials to reach them but who are "finding roads out." He said he'd heard reports of people hiking out of canyons.

In recent days, rescues in hard-to-reach areas have taken extraordinary measures. On Saturday a Chinook helicopter piloted by the Colorado National Guard picked up 78 children who got stranded while on a field trip.

Smith's hopeful tone was echoed by Boulder native Jake Koplen. His family nearly evacuated as floodwater surrounded his home. He snapped photos of the scene and posted them to CNN's iReport

Now his family is beginning the slow work of cleaning up. But they won't do it alone. Koplen says his phone has been ringing non-stop with offers of food and assistance.

Still, authorities worry that any additional water on ground that's already soaked by up to 15 inches of rain will cause more flooding and dislodge mud and debris.

Smith said he couldn't begin to estimate the scope of the damage. "I've known these areas for 25 years," he said "I don't recognize some of them."

Damage worth millions

Boulder County alone will need an estimated $150 million to repair 100 to 150 miles of roadway and 20 to 30 bridges, county transportation director George Gerstle said. The repair bill will be "10 to 15 times our annual budget," he said.

A helicopter surveillance mission Saturday carrying Colorado Gov. John Hickenlooper and members of Colorado's congressional delegation was diverted twice to pick up people waving to be rescued.

After the officials' delayed arrival at a Boulder airport, U.S. Sen. Mark Udall promised a bipartisan push in Congress for federal aid for flood recovery.

President Barack Obama signed a major disaster declaration for Colorado on Sunday and ordered federal aid to supplement state and local recovery efforts in Boulder County.

Hickenlooper said he spoke by phone with U.S. Transportation Secretary Anthony Foxx, who "was adamant that the $5 million that was released Friday was just the beginning" of federal assistance.

"We're going to come back and rebuild better than it was before," the governor said.

Already some are doing their own math. Barb Vacek doesn't know the dollar amount but she's taken stock of the emotional cost.

Her family is exhausted, their home and many of their mementos, gone. "I did lose my family slides from my parents who are deceased," she said. "I was the person entrusted with them, so my childhood is wiped out."

Right now, she says, her guilt outweighs her grief.