As Seminole County waited for the St. Johns River to crest in Sanford, homeowners throughout Central Florida saw their yards slowly fill with water from Hurricane Frances.

Officials from the National Weather Service said the St. Johns -- which drains the eastern half of Central Florida -- reached flood stage at Lake Harney on Tuesday and will flood at Sanford by tonight. Seminole County warned residents to consider evacuating low-lying areas.

Flowing at more than 4 million gallons a minute in some places, the St. Johns has risen almost 2 feet at Lake Harney since Sunday and more than 18 inches in Sanford, where the city issued a formal flood warning Tuesday. Although Sanford officials say it is unlikely water from Lake Monroe will come over the sea wall, the rise in the lake level could overwhelm its stormwater system.

Throughout the region, rivers, lakes and canals continued to swell, but flooding was isolated and mostly confined to low-lying roads and waterfront homes.

In Polk County, up to 20 homes in Peace River Estates No. 1 east of Bartow were flooded Tuesday by the Peace Creek, said Jeff Spence, Polk Natural Resources director.

In Volusia County, hard-hit areas such as Port Orange saw street flooding recede from a high of 4 feet to 2 feet. The city, overwhelmed by water from retention ponds, canals and creeks feeding into Spruce Creek, had flooding aggravated by a sewage spill from a pumping-station power failure.

In Port Orange's Cambridge neighborhood, several residents traveled down the street by canoe. One resident posted a sign reading: "Please, No Wake!"

In Ocoee in west Orange County, an eastbound lane of State Road 50 was closed because of 2 feet of water spilling from a pond, police Sgt. Randy Conyers said. Traffic backed up for 11/2 miles. The water was pumped out of the roadway by late afternoon, but the lane remained closed.

Along Big Sand Lake in Orlando's Dr. Phillips area, water stood 2 feet deep in the back yards of million-dollar homes. "Here we go again," said Phillips Landing resident Phil Ciarlo, who has complained for a year that broken lake berms have led to flooding.

In Osceola County, Poinciana Boulevard was closed from Reaves Road south to Pleasant Hill Road because of water damage. The road may be closed for up to 48 hours.

In Lake County, emergency officials were bracing for flooding along the St. Johns near Astor, where some neighborhood streets already are inundated and may be evacuated. Mascotte, Groveland and south Sumter County also are battling huge amounts of water flowing out of the Green Swamp.

Seminole County sent out reverse 911 calls on Tuesday to about 2,000 residents in low-lying areas, including Geneva, near Lake Harney, suggesting they prepare for a voluntary evacuation.

Larry and Denise Barnett, who live on Retreat Road west of Lake Harney, got one of the calls. The road was flooded so badly that some residents couldn't get out in their cars. Barnett has been able to get through the waters in his truck.

"It's going to get worse," Larry Barnett said. "It's going to be a wait-and-see kind of thing."

Lena Holton didn't want to bring her Ford Taurus through the water -- "It would be halfway up the doors." So to get her 8-year-old daughter Kayla to the doctor, she walked up to Mullet Lake Park Road and waited for a friend to pick her up.

The county closed Mullet Lake Park after floodwaters covered a boat ramp and part of the road. Seminole and Volusia counties also sought state authority to establish no-wake zones in the area to limit damage to homes that have rising water near them and to prevent boaters from hitting submerged docks.

The St. Johns River Water Management District was doing what it could to minimize flooding. Spokesman Hank Largin said the district was bleeding water out of the river system in Palm Bay and Lake Apopka. But that will not prevent flooding, he said.

"It's like there's asphalt everywhere. The ground is so saturated, the water just runs off very fast," he said.

Despite the rising waters, not many people were stopping to pick up sandbags given out in two Seminole County locations Tuesday. Residents could take up to 30 bags per vehicle.

It was too late for one of the parks-department workers handing out the sandbags. Earl Dawson, who lives near Lake Harney in Geneva, said his yard was already flooded.

"I just park at the road and wade to my house," he said.

Robert Perez, Rene Stutzman, Gary Taylor, Ludmilla Lelis, Melissa Harris, April Hunt, Robert Sargent and Christopher Sherman of the Sentinel staff contributed to this report. Sandra Pedicini can be reached at spedicini@orlandosentinel.com or 407-322-7669. Jim Leusner can be reached at jleusner@orlandosentinel.com or 407-420-5411.