Low-lying Oakport Township on the north side of Moorhead is in a desperate fight to try to save 500 of its 550 homes.
Township Chairman Greg Anderson says he knows of a few homes that have already flooded. About 50 homes in the township are thought to be safe.
Anderson says they need more volunteers, but that by the end of the day the rising water will leave few areas where it's possible to sandbag.
In Fargo, crews are working to shore up a clay dike in a south side neighborhood. Leanard Wollitz, who lives nearby, is worried about whether the dike will be ready in time. Wollitz also hopes the sandbag dike in his back yard will hold.
"I think there's probably about 2,000 sandbags back there, and we got a couple of sump pumps under the deck, in case water comes through," said Wollitz.
Just a day earlier, people in Fargo and Moorhead were being told all the sandbagging and dike building was nearly done. But the latest forecast has people scrambling.
Fargo Police Chief Keith Ternes says most earthen and sandbag dikes around the city are going to have to be raised another one to two feet -- to 43 feet high.
"That's what we're going to have to do for the next 48 hours," said Ternes. "To go one more foot takes a lot of work, a lot of bags. It's going to take over 300,000 bags in the next 24 hours."
Officials say that number will grow to half a million sandbags before the weekend. Fargo Mayor Dennis Walaker says the city is entering uncharted territory, and he expects residents to prepare for the worst.
"You need to take your valuables, things that you can't replace, and move them up, no matter where you are in the city. It's easy to take them back down after the event," said Walaker. "We need everybody in the community to take this very seriously, because we've never gone above 40 feet in the last 112 years."
Walaker says the remaining hours before Saturday's crest will be an intense push in miserable conditions.
“We need everybody in the community to take this very seriously, because we've never gone above 40 feet in the last 112 years.”Fargo Mayor Dennis Walaker
"We're talking about freezing temperatures. We're talking about the flood crest getting up to 40 feet by Friday and 41 feet by Saturday," he said. "We have a lot of things we have to top off, we have to build contingency dikes and we need the volunteers to continue their process."
City crews, the North Dakota National Guard and the Army Corps of Engineers are busy putting up as many contingency dikes as they can, in case the primary dikes fail.
Across the river in Moorhead, officials aren't planning to build more contingency dikes. But engineers are working around the clock to make sure the city's dike system is solid. Moorhead is also adding another two feet to its dikes.
City Manager Mike Redlinger says Moorhead will desperately need more volunteers to fill sandbags over the remaining hours.
Redlinger says it's important the dikes are solid, because the water is expected to remain high after it crests.
"We're going to really have to be able to sustain four, five, maybe even longer ... days of a sustained crest," said Redlinger. "So that really speaks to the importance of dike integrity, and making sure we do everything we can to try and make sure we catch any problems with leaks as early as we can."
A nursing home facility in Moorhead plans an early evacuation of some 400 elderly residents. People who care for vulnerable adults and those who need extra care are being asked to evacuate those residents as well.
Officials in both Fargo and Moorhead say it's too early to talk about a mass evacuation, but plans are in the works.
Minnesota Gov. Tim Pawlenty has asked for an expedited federal disaster declaration for seven northwestern Minnesota counties. Several members of Minnesota's congressional delegation met with President Obama Wednesday to make the case.
An early declaration would free up millions of dollars in federal assistance for flood recovery.
Obama has already approved a disaster declaration for North Dakota.
*Volunteers can report to the Fargodome in Fargo, or in Moorhead, at the Nemzek Hall at Minnesota State University, Moorhead. For more information about how to volunteer, call 701-476-4000.
(The Associated Press contributed to this report)