FARGO, N.D. — Salesmen in Fargo are hawking products with names like the Muscle Wall and the Sandbagging Buddy. Emergency workers in Keokuk, Iowa, are planning to barricade the water treatment plant with limestone boulders. The farmers’ cooperative in Quincy, Ill., is moving grain inland to keep it dry.

Spring could bring disastrous flooding again to the Upper Midwest, government forecasters are warning. And folks along the Red, the Mississippi and the Missouri rivers are taking precautions, especially after calamities last year and the year before.

“This is like having a two-month warning that a tornado is going to hit your house,” said Richard Thomas, who lives near Fargo. “There’s always the possibility we’ll be just fine, but it’s bothering me. It’s stressful.”

The National Weather Service said heavy snow cover and ground that is already saturated could lead to severe flooding in as little as a few weeks. Exactly how severe will depend on how fast the snow melts and how heavy the spring rains are.

In Fargo and neighboring Moorhead, Minn., an area of about 200,000 people, the chances of major flooding were projected Friday at about 90 percent. The probability of record flooding was put at 19 percent. Elsewhere across the Upper Midwest, the threat is less dire but still serious.

In dozens of towns from Missouri north through the Dakotas to the Canadian border, homeowners, farmers and business owners are putting aside normal business to deal with a hazard they know all too well.

During March and April last year, rivers and streams burst their banks in North Dakota and Minnesota, forcing millions to evacuate, damaging hundreds of homes and causing an estimated $100 million in damage. At least three deaths were blamed on the rising waters. Fargo and Moorhead stacked 6 million sandbags to hold off the Red River, which lapped to within 6 inches of the top of the floodwall, breaking a record set in 1897.

“I think people are still shell-shocked from last year,” said Cecily Fong, spokeswoman for the North Dakota Emergency Services Department.

Clarksville, Mo., a town of about 500 people whose downtown antiques shops and other businesses lie close to the Mississippi, plans to construct a levee using sand-filled metal bins. The bins are then covered with plastic and sandbags.

“Are we panicked? No. Did we learn a lot in 2008? Yes. Are we prepared? I hope. And we have a plan,” said Mayor Jo Anne Smiley.

The downtown part of Quincy, Ill., is safely perched on a bluff, but the sewage plant on lower ground was almost swallowed up in a flood in 2008. Emergency managers there are now reviewing flood-response plans and checking the condition of the area’s dikes.

Some of the 4 million bushels of grain stockpiled in a World War II-era river terminal in Meyer, Ill., are being sent to storage sites inland, said Gerald Jenkins, overseer of the Ursa Farmers Cooperative. But he said it can’t all be moved to safety in time. Ice jams on the Mississippi slowed barge traffic this winter, and repairs have shut down a lock and dam.

“It is scary, and there are just a certain number of things you can do,” he said. “We just hope the conditions all work out, which they do 19 years out of 20.”

Officials in Keokuk, Iowa, are testing pumps and emergency equipment and planning to haul large rocks from a quarry to protect the water treatment plant.

Folks in Fargo are beginning 12-hour shifts building sandbag barriers as thick as castle walls. Three machines called “spiders,” each with 12 funnels, fill 5,000 bags an hour. Two hundred shovels are ready for volunteers filling bags the old-fashioned way.

Other labor-saving products offered for sale include the Muscle Wall, a water-filled plastic barricade that is supposed to make sandbags obsolete, and the funnel-like Sandbagging Buddy, used to fill bags rapidly.

Across the Red River in Minnesota’s Oakport Township, workers using backhoes, bulldozers and dump trucks will build more than six miles of temporary clay levees.