Residents braced for an aftermath forecast expected to include overflowing rivers and flooded basements. Flooding was also being fueled by unseasonably high temperatures that climbed into the 60s in Illinois.

In Kane County, several dozen Boy Scouts spent Saturday morning filling 2,400 sandbags for residents to pick up as needed outside the Campton Township Highway Department. Scouts shoveled sand into the bags and stacked them in neat piles.

"They're learning community service," said troop leader Jeff Koehl, who said authorities sent out an e-mail asking for Scouts to volunteer. "They're just concerned with the way we're going to get this quick melt that all the tributaries are going to fill up."

In the Chicago suburb of Riverside, authorities encouraged residents along the Des Plaines River to evacuate, saying the river was expected to rise to nearly 10 feet by Sunday morning.

Nature dealt Illinois a mixed bag of weather on Saturday, with flood warnings and advisories in the north and tornado watches in the central and southern parts of the state.

A powerful storm system swept across a wide swath of south and central Illinois during the afternoon, packing wind gusts of 60 to 70 mph, said National Weather Service meteorologist Patrick Bak. The storms also produced hail, and the Weather Service office in St. Louis received reports of funnel clouds.

The storms damaged buildings and brought down tree limbs and power lines. In Sangamon County, high winds blew off a large section of a school district administrative building roof in Springfield.

In the Chicago area, power restoration was being slowed by flooding at utility substations, said ComEd spokesman Jeff Burdick.

Winds knocked out power to more than 60,000 ComEd customers Saturday, Burdick said. Most had power restored by Saturday evening, and crews were working to restore service to the rest.

Thousands of people lost power elsewhere in Illinois.

In Chicago, crews turning Wrigley Field into an ice rink for the upcoming National Hockey League's Winter Classic removed snow from the stadium Friday. Who knew rain would have washed it away the next day?

Illinois Emergency Management Agency spokeswoman Patti Thompson said Saturday that the agency was in "readiness mode" and making sure local officials are aware of the flooding advisories.

In Cook County, authorities began monitoring river levels Friday and offered sandbags to communities in case they needed to fortify low-lying areas.

Winnebago County in northern Illinois was also offering sandbags to residents concerned about the rising Rock River. Water covered parts of Interstate 80 near the Iowa border Saturday afternoon, forcing the Illinois State Police to close portions of the road and detour traffic.

The Weather Service forecast widespread and "potentially significant" flooding. Meteorologists said the melting snow, heavy rains and frozen ground could combine to flood areas where high water is rare.

"The potential exists for serious and potentially life threatening flooding to develop with some areas that typically do not flood, possibly even becoming inundated with water," the Weather Service said in an advisory.

The weather caused 90-minute delays at Chicago's O'Hare International Airport and forced the cancelation of more than 150 flights. Sunday is expected to be O'Hare's busiest day of the holiday travel season, aviation officials said.

The National Weather Service also reported Saturday that 2008 has been the wettest year on record for the city of Chicago, with just under 50 inches of precipitation.

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Associated Press writers Karen Hawkins and Rupa Shenoy contributed to this report.