A massive flood in Minnesota and surrounding states was “sitting on our doorstep,” but the chilly March weather and lack of rainfall kept it at bay.

Even so, the threat of substantial flooding could return quickly if April brings more snow or heavy showers.

“We had probably the biggest potential flood sitting on our doorstep,” Craig Schmidt, a senior service hydrologist with the National Weather Service (NWS) in Chanhassen, said Monday. “If you want to see how bad it could have been, look at Nebraska and Iowa.”

The region experienced above-average snowfall, and much of it fell in a six-week period in January and February, Schmidt said. What’s more, the extreme cold in those months meant that every flake stayed.

“Not only did we have deep snow, but it was so extensive,” he added. “It covered all of Minnesota, all of Wisconsin. Every river was a potential problem.”

The slow and steady March thaw, coupled with an extremely dry stretch of days with little to no precipitation, saved the day, keeping the snow from melting too quickly, overwhelming streams and rivers.

“To get two to three weeks of no rain in March is almost unheard of,” Schmidt said. “It just doesn’t happen that often. It was the last thing I would have expected.”

Despite the almost ideal melt, he said, we’re not yet off the hook.

Although many rivers in the southern half of the state are cresting and receding, they will all remain swollen and will be moving a lot of water for some weeks to come.

“Through the whole month of April, we still will be vulnerable to heavy rain,” Schmidt said. “We’re not completely out of the woods. I want to make sure people are aware of that.”

In St. Paul, the Mississippi River crested Sunday night at just under 20 feet at the Robert Street bridge, said Rick Schute, the city’s director of emergency management. Major flood stage is 17 feet.

About a dozen low-lying city parks are closed, including Harriet Island, Hidden Falls, Upper and Lower Landing, and Raspberry Island. Schute said the city will work to get the parks reopened as quickly as possible after the water’s expected drop-off in about a week, but he said the parks won’t be open until they can be properly cleaned up.

Roads now underwater need to be thoroughly checked for integrity, he added.

Up North, snow and ice in the Red River Valley are just beginning to break up, with rivers and tributaries starting a slow rise. But as in much of southern Minnesota, the relatively mild March, with daytime temperatures above freezing and nighttime temperatures below 32 degrees, has led to a gradual melt and kept flooding to minor levels so far.

In Fargo, city officials called a halt to sandbagging preparations. With about 400,000 bags already filled, city officials believe they have enough to deal with any emergency need, said City Engineer Nathan Boerboom.

The Red River is expected to crest in Fargo next Monday at about 34 feet. As recently as five days ago, emergency crews were preparing for a crest of 41 feet, but the spring’s “ideal melt” has eased concerns, Boerboom said. The Red crested at a record 40.84 feet in Fargo in March 2009.

“We’re still looking at a lot of water going through town,” he said. “We have identified the areas where we need temporary levees, and we have all the resources deployed.”

Along the Red River, which flows north into Canada and forms the border between Minnesota and North Dakota, the thaw is “coming in chunks,” said Greg Gust, warning coordination meteorologist with the NWS in Grand Forks.

Many of the Red’s tributaries on the Minnesota side have begun dumping their water into the main stem, but the North Dakota side “is going to wake up this week,” he said.

The threat along the river system’s main channels is down, Gust said, but rural areas could see local flooding of ditches and roads.

In terms of the actual volume of water moving through the system, this year’s melt could be among the Top 10 ever, Gust said.

“It’s just coming a little more spaced out,” he said. “Now we’re starting our third week of a perfect thaw. It’s had that two, almost three weeks to start edging things through.