The Red River has risen rapidly in the past 24 hours and is on track for a crest late this weekend.
Officials with the National Weather Service say the water will reach 39 to 41 feet, making it one of the top three floods for the Fargo-Moorhead area.
Weather Service officials say the crest could coincide with a storm system that will bring rain to the region Saturday into Sunday.
Forecaster Mark Ewens said there's a good possibility of rain with the threat of thunderstorms.
"There is still a fair amount of snow in places," Ewens said. "[We're] going to have two nice warm days that's going to finish off the melt in a lot of spots where it hasn't gone."
Ewens said if the precipitation falls in a relatively small area the impact will be minimal, but if it is widespread that will have an impact on the eventual crest.
"[If] we get a quick three-quarters of an inch — and again with thunderstorms that's always a tricky part because you can get more," he said.
City officials in Fargo and Moorhead encouraged volunteers to show up Wednesday to help place temporary sandbag dikes. About 120 people showed up Tuesday. Wednesday, volunteer coordinators expect a few larger groups but they're still calling for individuals to help.
Fargo Deputy Mayor Tim Mahoney said that because of the weather, they aim to have everything in place by Friday night.
"I think we're going precision flood fighting now where we're trying to minimize how much work we have to do because we did a lot getting to this point," Mahoney said. "So the word for the day is stand up and be counted. If we do not get enough volunteers we will do code reds, and if you get one in your neighborhood you're expected to come and help."
Moorhead's Mayor Mark Voxland is concerned that people are putting things off.
"I've done flood fighting for years; I'm still amazed at how many people that live along the river are not worried about sandbagging yet," Voxland said. "If everyone decides Saturday afternoon ... is the time they want to start, you may not see your sandbags until the next day."
About 500 homes in the area need sandbag protection from flood waters.
Clay County Sheriff Bill Bergquist says motorists should stay alert to conditions on rural roads.
"Not even if there's not water over them with all the water in the ditches the shoulders are really soft," Bergquist said. "We've had vehicles we've had to pull out of ditches full of water already. Please stay off them if you can."