BATON ROUGE, La. - Thousands of people in southern Louisiana hunkered down in shelters Monday, forced out of their homes by intense flooding that took many people by surprise.

The weather had improved from the torrential downpours, but rivers and creeks in many areas were still way above flood stage, and people downstream eyed the deluge with concern.

Across southern Louisiana, residents scrambled to get to safety as heavy rain in some areas came close to 2 feet over a 48-hour period. Rescuers evacuated more than 20,000 people since the flooding started Friday, and more than 10,000 people were in shelters as of late Sunday, according to Louisiana Gov. John Bel Edwards. At least six people were killed.

"Everybody got caught off-guard," said Anthony "Ace" Cox, who started a Facebook group to help collect information about where people were stranded. "It was an absolute act of God. We're talking about places that have literally never flooded before."

Cox lives in New Orleans but his parents live in Central, a town hit hard by the rising water. His parents evacuated to his grandparents' house in Baton Rouge, but that area started taking on water, so they evacuated again to a hotel in Baton Rouge.

He is worried that his parent's home may not be habitable for months.

Meteorologist Ken Graham of the National Weather Service said catastrophic rains are "extremely tough" to forecast.

Forecasts Thursday were for 8 inches of rain, with higher totals expected in some areas, but again, Graham emphasized that forecasting exactly how much rain is going to fall is nearly impossible - "especially for a historic event."

"It's one thing to say we're getting set up for a lot of rain. It's another thing to say where is this going to be," Graham said.

Some areas such as the town of Zachary received more than 2 feet of rain in a 48-hour period that ended Saturday morning. Another hard hit area - Livingston - received nearly 22 inches of rain over the same stretch.

National Guard soldiers in high-water vehicles, boats and helicopters helped rescue people, as did Good Samaritans.

Jared Serigne of St. Bernard Parish helped organize volunteer efforts involving roughly 70 experienced boaters who rescued hundreds of people from flooded communities such as Monticello, St. Amant and Port Vincent.

He criticized the government's response, saying officials were slow to clear roadways and to provide access to potential boat launch points that could be used by volunteers.

"You've got all of these people who hunt and fish who have more experience than the average first-responder," said Serigne, a TV producer of an outdoors show and marketing director for marine equipment business.

The Louisiana State Police started allowing people to reclaim cars left behind on a portion of Interstate 12 that had to be shut down because of the flooding. Motorists had in some instances been stranded overnight awaiting rescue.

Vehicles that were out of gas, stalled or unclaimed were being towed Monday to the shoulder to help clear the interstate.

From the air, homes looked more like little islands surrounded by flooded fields. Streets descended into impassable pools of water, and shopping centers were inundated with only roofs of cars peeking above the water.

From the ground, it was just as bad.

The slow-moving, low-pressure system moved into Texas, but the National Weather Service warned there's still a danger of more rain and fresh floods, as swollen rivers drain toward the Gulf of Mexico.

Rivers in the Baton Rouge area have started to fall but still remained above flood stage after setting record levels over the weekend, the National Weather Service said Monday.

"The rivers and streams north of Interstate 12 have crested and have started to drop, while those south of the interstate continue to rise," meteorologist Mike Efferson said.

Adding insult to injury, it started raining in Baton Rouge again Monday, and the city could see up to a half-inch of precipitation.

The Comite River just east of Baton Rouge dropped nearly 2 feet by Monday from the 34-feet over the weekend; flood stage is 20 feet. The Amite River at Denham Springs was at 43.5 feet Monday after reaching 46.2 feet; flood stage is 29 feet.

The federal government declared a major disaster, specifically in the parishes of Tangipahoa, St. Helena, East Baton Rouge and Livingston.

Many of the homeowners who live in areas inundated with floodwaters have no flood insurance, a problem that will leave them draining savings accounts and relying on federal disaster programs to rebuild and repair.

Insurance Commissioner Jim Donelon said that in hard-hit Baton Rouge, only 12 percent of residences are covered by flood insurance. The numbers "were really shocking," he said.

The evacuees included the governor and his family, who were forced to leave the Governor's Mansion when chest-high water filled the basement and electricity was shut off.

Noel Michael, a school teacher, and her husband, Deryl, a retired Marine, spent Saturday piling sandbags around their home in the Livingston Parish town of Walker, but it became fruitless.

"It was like a waterfall," she said.

They escaped in her husband's pickup - he was behind the wheel and she was on the hood, helping navigate.

They took refuge at her parents' house in Livingston, but they didn't rest long.

On Monday morning they were at one of a chain of area grocery stores run by family friends, helping clean up and re-stock shelves while managers called suppliers and warehouses, hoping trucks could get to them to replenish meat, poultry and milk while flood-weary residents lined up outside.

"My husband and I just said, 'You know, we can sit here and cry, or we can help clean up,' " Noel said in a telephone interview, her voice breaking. "We're able-bodied. This can get our mind off things."