Last Updated Aug 28, 2017 9:20 AM EDT
HOUSTON -- The remnants of Hurricane Harvey continued dumping historic levels of rainfall on the Houston area Monday morning as devastating floods swamped the nation's fourth-largest city. Rising water chased thousands of people to rooftops or higher ground and overwhelmed rescuers who could not keep up with the constant calls for help.
The National Weather Service says flooding isn't expected to peak until Wednesday or Thursday.
"We are not out of the woods yet," Elaine Duke, Acting Secretary of the Department of Homeland Security, said at a Monday morning briefing. "Harvey is still a dangerous and historic storm."
The incessant rain covered much of Houston in gray-green floodwaters and turned streets into rivers navigable only by boat. In a rescue effort that recalled the aftermath of Hurricane Katrina, helicopters landed near flooded freeways, airboats buzzed across submerged neighborhoods and high-water vehicles plowed through water-logged intersections. Some people managed with kayaks or canoes or swam.
Volunteers joined emergency teams to pull people from their homes or from the water, which was high enough in places to gush into second floors. The flooding from Harvey, which made landfall late Friday as a Category 4 hurricane and has lingered dropping heavy rain as a tropical storm, was so widespread that authorities had trouble pinpointing the worst areas. They urged people to get on top of their houses to avoid becoming trapped in attics and to wave sheets or towels to draw attention to their location.
Rescuers had to give top priority to life-and-death situations, leaving many affected families to fend for themselves. And several hospitals in the Houston area were evacuated due to the rising waters.
Judging from federal disaster declarations, the storm has so far affected about a quarter of the Texas population, or 6.8 million people in 18 counties. It was blamed for at least two deaths.
As the water rose, the National Weather Service issued another ominous forecast: Before the storm is gone, some parts of Houston and its suburbs could get as much as 50 inches of rain. That would be the highest amount ever recorded in Texas.
"The breadth and intensity of this rainfall is beyond anything experienced before," the National Weather Service said in a statement.
The director of the Federal Emergency Management Agency (FEMA), Brock Long, predicted that the aftermath of the storm would require FEMA's involvement for years. "This disaster's going to be a landmark event," Long said.
Follow along below for live updates on the storm. All times are Eastern unless otherwise noted.
8:40 a.m.: President Trump approves Louisiana emergency declaration
A statement from the White House Monday said President Donald Trump has declared an emergency in Louisiana, authorizing federal assistance for Harvey relief efforts in the state.
The statement said the Department of Homeland Security and FEMA would coordinate disaster relief efforts "to save lives and to protect property and public health and safety, and to lessen or avert the threat of a catastrophe in the parishes of Beauregard, Calcasieu, Cameron, Jefferson Davis, and Vermillion."
7:30 a.m.: 30,000 people expected in emergency shelters
In a Monday morning briefing, FEMA Administrator Brock Long said officials are expecting 30,000 people in emergency shelters. As many as 50 counties are feeling the impact of the storm.
Calling Harvey a "landmark event," Long said "you could not dream this forecast up."
When it comes to the emergency response and evacuations, Long said he believes local, state and federal agencies thus far have operated with the "best information that they had at the time." More widespread evacuations would have been "difficult" given the time frame, putting people at risk of becoming trapped in long lines of vehicles trying to escape rising floodwaters, which would have been worse than the shelter-in-place scenario playing out now.
"All disasters begin and end at the local level," he added. "All evacuation decisions are made at the local level in Texas."
"We are not out of the woods yet," said Elaine Duke, Acting Secretary of the Department of Homeland Security. "Harvey is still a dangerous and historic storm."
Duke said emergency officials are currently focused on rescue efforts and plan to move into recovery mode later this week.
For now, she urged local residents to avoid calling 911 unless they were in need of urgent, immediate medical assistance.
Duke said she will accompany President Trump as he visits Houston on Tuesday.
According to the latest forecast from the National Weather Service, the storm is expected to dump another 15 to 20 inches of additional rainfall on the region before it's over.
Long encouraged Americans who want to help storm victims to go to the website www.NVOAD.org to connect with National Voluntary Organizations Active in Disaster, which is coordinating donations and volunteers.
Those in need of assistance should visit www.disasaterassistance.gov if they have internet access or call 1-800-621-FEMA.
6:50 a.m.: Louisiana seeks emergency declaration
Louisiana's governor is asking President Trump for a federal emergency declaration for Louisiana since forecasters expect Harvey to cause significant damage in the state.
Gov. John Bel Edwards said he sent a letter to the White House requesting the initial disaster declaration for five parishes in southwest Louisiana, and could add more areas to the request later.
Edwards said life-saving efforts such as search and rescue and shelters will be needed, especially in southwest Louisiana where forecasters say 10 to 20 inches of rain could fall.
5:15 a.m.: Harvey almost standing still
Harvey continues to head back toward the Gulf of Mexico at a slow pace.
The National Hurricane Center said in its 4 a.m. CDT update that the tropical storm still has sustained winds of up to 40 mph and is centered 20 miles east of Victoria, Texas, about 120 miles southwest of Houston. It continues to creep to the southeast at 3 mph.
That means it remains virtually stalled near the coast and continues to drop heavy rain on the Houston and Galveston areas. In the past 48 hours, numerous spots in the region have measured more than 25 inches of rain.
The hurricane center says Harvey's center was expected to drift off the middle Texas coast Monday and meander offshore through Tuesday before beginning "a slow northeastward motion."
The center says people in the upper Texas coast and in southwestern Louisiana should continue to monitor Harvey's progress.
3:38 a.m. Dealing with rescue requests
Houston officials continue to urge people to shelter in place and stay off flooded roadways as Harvey continues to batter the nation's fourth-largest city.
Public Information Officer Keith Smith also says Sunday that rescue efforts continue and now are focused on those who feel trapped inside a home or building.
Smith says the city's 911 emergency response system has been challenged by sharply increased call volumes since the tropical storm made landfall late Friday.
4:37 a.m. Power outages grow
Some 269,000 homes and businesses were in the dark in Southest Texas early Monday due to Harvey, utilities reported.
3:25 a.m. Evacuees sheltered in convention center
Hundreds of people affected by devastating flooding in Houston have flocked to a downtown showcase convention center-turned-emergency shelter. Many arrived Sunday carrying little more than what was in their pockets. Most are preparing for a stay of several days, as water rises inside their homes and roads remain impassable.
he American Red Cross was expanding the shelter by the hour. Volunteers initially set out around 1,300 cots and quickly assembled more in anticipation of other evacuees arriving through the night. They have enough space and cots to house 5,000 people.
3:20 a.m. Post Office pulls back in Houston
2:15 a.m.: Reservior water releases
Residents living around the Addicks and Barker reservoirs designed to help prevent flooding in downtown Houston, were warned Sunday that a controlled release from both reservoirs would cause additional street flooding and could spill into homes. Rising water levels and continuing rain was putting pressure on the dams that could cause a failure without the release.
Harris and Fort Bend county officials said Sunday that residents around certain areas should be prepared for the influx of water that was scheduled to happen at Addicks around 2 a.m. local time Monday and a day later at Barker. Officials warned residents they should pack their cars Sunday night and wait for daylight Monday to leave.
Thousands of homes could be affected by the releases, CBS Houston affiliate KHOU-TV reports.
2:45 a.m. Evacuations ordered outside Houston
Meanwhile, officials in Fort Bend County, Houston's southwestern suburbs, late Sunday issued widespread mandatory evacuation orders along the Brazos River levee districts. County officials were preparing for the river to reach major flood stages late Sunday. County Judge Robert Herbert said at a news conference that National Weather Service officials were predicting that the water could rise to 59 feet, three feet above 2016 records and what Herbert called an "800-year flood level." Herbert said that amount of water would top the levees and carries a threat of levee failure.
12:15 a.m. More National Guard members
Texas Gov. Greg Abbott says another 1,000 National Guard members will be sent to Houston on Monday as flooding from Harvey continues to ravage the area. The governor announced the move late Sunday on his personal Twitter account.
Earlier Sunday, Abbott said the state activated 3,000 National Guard and State Guard members as a result of the storm damage. He also said 500 vehicles and 14 aircraft had been put into service.
11:50 p.m.: Hurricane Harvey Relief Fund
Houston Mayor Sylvester Turner established the Hurricane Harvey Relief Fund that will accept tax deductible flood relief donations.
"We are getting calls from across the country and right here in our hometown, and the generosity of people who understand this disaster is truly amazing," Mayor Turner said. "Together we can make a difference to those who will need extensive help to get back on their feet once this storm is over."
Here are ways to donate:
Online Credit Card Donations: Visit www.ghcf.org. Online credit card donations will be assessed a small fee, typically 3 percent, by the credit card companies. Donors have the option of increasing their credit card donations to cover this fee.
Checks/Money Orders: Mail to Greater Houston Community Foundation, 5120 Woodway Drive, Suite 6000, Houston, TX 77056.
Transfer Cash by Wire: Wire To:
JP Morgan Chase Bank, N.A.
ABA # 021000021
For credit to: Greater Houston Community Foundation
For further credit to: Hurricane Harvey Relief Fund