OWATONNA, MINN. - As floodwaters began to recede in some places Friday, public officials, homeowners and farmers across a wide swath of soggy southern Minnesota began assessing the damage from what climatologists called "the largest flood event" to hit the area in three years.

As of late Friday afternoon, a flood warning from the National Weather Service remained in effect for much of southern Minnesota, including the Twin Cities.

The Weather Service also forecast that the Mississippi River in St. Paul may see flooding next week, prompting city officials to announce road closures near the river starting Monday. State officials said that although the risk of flash flooding has decreased, there is a chance that as high water flows downriver, more communities could face flooding.

Gov. Tim Pawlenty said Friday that he intends to call a special session of the Legislature to address state aid to those who suffered damage. The session, probably no longer than a day, will be held after federal officials complete their assessment of the destruction.

The most dramatic flooding followed heavy rains that fell on the southern tier of the state Thursday night. Six or more inches of rain hit numerous areas -- the highest totals were 10.68 inches in Amboy in Blue Earth County and 10.2 inches at Truman in Martin County -- feeding floodwaters that submerged roads and bridges, filled basements and choked off access for emergency workers.

By Friday afternoon, local officials were requesting state and federal aid to rebuild washed-out roads and bridges and damaged businesses. Local and state officials said it's still to early to attach a dollar figure to the total damage.

Pawlenty, who visited hard-hit areas Friday with Kris Eide, his emergency management director, praised the "great teamwork" of emergency responders and ordinary people for helping prevent the loss of life. "This is a very significant event," he said of the rapid rise of floodwaters. "It's a dramatic amount of water that's hit the ground in a short time."

The governor declared a state of emergency in 34 counties. He said that FEMA will begin assessing damage Monday morning and that he is confident the area will qualify for federal assistance.

"We will make the request to President Obama to issue a national disaster declaration," Pawlenty said.

Mike Johnson, Steele County's emergency manager and Owatonna's fire chief, said there must be a total loss of $6.4 million from a single event for Minnesota to qualify for federal disaster assistance. It's likely that threshold will be reached, he said. "It's actually an advantage for everybody that the flood has hit so many areas," he said of getting federal aid.

On his weekly radio show Friday, Pawlenty said state officials will "make sure we're doing all we can to help these communities." The flooding, he said, "is another example when Minnesotans are going to have to rally to help each other."

Water world

At least 70 Owatonna homes were evacuated, and about 55 troops from the Minnesota National Guard were sent to Owatonna to provide assistance. Interstate 35 was closed for several hours Friday as traffic was detoured away from the high water. Even the homecoming football game and parade set for Friday in Owatonna had to be postponed.

In Truman, floodwater filled the basements of most of the town's homes and made normally narrow Maple Creek as wide as a football field. At the Owatonna offices of American Rental, three buildings, five trucks, more than a dozen trailers and a 37-foot lift were underwater. The company ferried employees to work in a fishing boat.

"It's sad. We are taking computers out of the warehouse by boat," said Pat Doyle, a manager. "I have never seen anything like this."

Officials say the Straight River was 2 feet higher than normal Friday.

Rare fall storm

Heavy-hitting storms are not the norm in autumn, said Pete Boulay of the Minnesota State Climatology Office. But they aren't exactly unheard of. In the fall, he said, the jet stream shifts to a similar path as in the spring. If that air hits moist Gulf of Mexico air -- or the remnants of a hurricane -- heavy autumnal rains can follow. That can lead to rapid flooding.

"It does happen," Boulay said of the rains -- and the floods. The last time it happened, he said, was in October 2005. Overall, the storms were the biggest to hit this part of the state since August 2007, he said.

Damage to crops and fields in Martin County, which appears to have been the hardest hit by the floodwaters, is not considered catastrophic. Hopes for an early harvest have been dampened, said Larry Bremer of the Farm Service Agency in Fairmont. But much of the corn and soybean crop is expected to survive.

State parks and trails in the region also felt the effect, with a host of closures announced by the state Department of Natural Resources. They included the Minnesota Valley State Trail; the Snake Creek and Trout Valley OHV (off-highway vehicle) state forest recreation areas; the campground at Beaver Creek Valley State Park and a few campsites at Whitewater State Park.

As of Friday afternoon, the Straight River continued to be troublesome. High water closed bridges over the river, gumming up traffic. It was a reminder that, for some, the effects of the flood won't recede as quickly as the water.

Hamid Torabpour, 26, his pregnant wife, Camille, and their three children were forced out of their Owatonna home by basement flooding. Torabpour said their home sustained an estimated $60,000 in damage and they lost $25,000 worth of belongings, including 90-year-old family photographs. On Friday, they came to the airport hoping to tell their story to Pawlenty.

"Before this," Camille Torabpour said, "we'd never had more than a puddle in our basement."

The Associated Press contributed to this report. pwalsh@startribune • 612-673-4482 plevy@startribune.com • 612 673-4419 jwalsh@startribune.com • 612-673-7428