More than 1,000 residents are stranded in the wake of ferocious flooding and relentless rain that have killed at least five people and left 19,000 homes in Colorado either damaged or destroyed, according to officials.
A total of 1,253 people are also unaccounted for but officials cautioned the number is subject to change as widespread flood recovery efforts continue. The Colorado Office of Emergency management reports that five people, four in Boulder and one in El Paso County, are dead.
Nick Christensen of the Larimer County Sheriff's Office says that with so many missing, the number of dead will likely rise.
"It's just going to take some time to determine the status of everybody," he said.
A National Guard helicopter carrying civilians out of Lyons, Colo., was grounded by heavy rains and flood waters Sunday. The crew has been forced to wait it out and spend the night on higher ground, according to a National Guard news release. It's just another problem in a continuous stream of misfortune for so many in the flood zone.
As many as 1,000 people in Larimer County were awaiting rescue Sunday, but airlifts were grounded because of the rain, Type 2 Rocky Mountain Incident Management Team commander Shane Del Grosso said, according to The Associated Press.
The stranded are without power and are thought to be low on food. Del Grasso says they need a break in the weather to continue rescue efforts.
"We need a change in the weather pattern to get a break and to really go after what needs to be done out there," Del Grosso told ABC News Radio.
A total of 20 military helicopters and crews were scheduled to conduct evacuation operations Sunday. Most were grounded as heavy rain and low ceilings hampered visibility, according to the National Guard.
The National Guard is working overtime and has conducted at least 400 helicopter rescues in what is now the largest aerial rescue operation since Hurricane Katrina in 2005.
Days of punishing rain and floods have transformed the mountain communities in Colorado's Rocky Mountain foothills from a paradise for backpackers and nature lovers into a disaster area with little in the way of supplies or services.
Roadways have crumbled and scenic bridges have been destroyed since the flooding began Wednesday.
The flood waters are covering more than 2,000 square miles across 15 counties in Colorado, an area about twice the size of Rhode Island. More than 11,000 people have been evacuated and there are still several evacuation orders still in effect.
Meanwhile, schools will be closed today in districts affected by the flooding.
The additional rain falling on ground that has been saturated by water since last week has left many people fearing that more flash flooding and mudslides could still happen.
"We're tied in with hydrologists and stream flow people who are monitoring the currents as we speak because that was one of our concerns, is you know, are we going to get new flooding," Del Grosso said.
Thunderstorms are expected again in Colorado and New Mexico today and rainfall is not anticipated to let up until at least Tuesday, when drier air is expected to reach the area.
Meanwhile, in the neighboring state of New Mexico, another round of rain moved across the state Sunday, renewing the threat of heavy runoff from already saturated soils and flooding in low areas as residents faced a major cleanup effort from damage left in the wake of days of persistent rain.
President Obama signed a major disaster declaration this weekend, ordering federal aid for the flood-ravaged state.
5th-Graders Rescued From Deadly Floods
Eighty-five fifth-graders and 24 adults from Fireside Elementary in Louisville, Colo., were in the mountains near Jamestown on a school trip when the heavy rains began Wednesday.
The outing turned into a three-day ordeal after the heavy rain caused mudslides and the road back to the camp was swept away. The students, teachers and chaperones were forced to hunker down, but the adults say the children looked out for each other.
"It was pretty cool to then see their friends rally around them and be like, 'Hey, talk to me. What's going on? I'm here for you,'" said Holly Gawley, a mother and chaperone.
Back in Louisville, frantic parents were desperate for news.
"There wasn't a lot of information coming out which was the hardest part," Kate Kaufman said.
The National Guard was able to land a helicopter nearby Saturday and pluck everyone off the mountain safely.
"You want your kid to be on the first bus so they can come home and then the second bus and then the third bus and then she came off on the fourth bus and I just never been so happy," said Danna Hinz, who was reunited with her daughter.
ABC News' Sam Champion, Clayton Sandell, ABC News Radio and The Associated Press contributed to this report.