Reports: Harvey's unrelenting rain triggers deadly, unprecedented flooding across Houston

As Harvey continues to dump heavy rainfall over Texas, southwestern Louisiana now faces a threat of flooding from the slow-moving storm.

The former Category 4 hurricane has battered the Texas coast with destructive winds and drenching downpours following landfall on Aug. 25. Widespread and unprecedented flooding is ongoing in the Houston, Texas, area, with thousands of water rescues completed and tens of thousands of 911 calls placed.

In addition to the devastating flooding in southern Texas, there have also been widespread power outages, isolated tornadoes and at least five reported deaths as of Sunday.

Harvey is the first major hurricane to impact the United States since Wilma in 2005.

Donate now to the United Way to help Harvey victims.

9:50 p.m. CDT Sunday: Thunderstorm gusts have been reported of 63 and 70 mph around Dalhart, Texas, within the last hour.

Creek crest Harvey 8.27.17

The Cypress Creek near Westfield, TX is expected to crest 8.4 ft above the 1949 record crest early this week. (Photo/NOAA)

8:43 p.m. CDT Sunday: A flash flood emergency has been issued for Houston and surrounding areas until 1:15 a.m. Monday.

Near Sugar Land, Texas, about 30 minutes southwest of Houston, 4-5 inches of rain per hour is currently falling.

Harvey highway flooding

Two people walk down a flooded section of Interstate 610 in floodwaters from Tropical Storm Harvey on Sunday, Aug. 27, 2017, in Houston, Texas. (AP Photo/David J. Phillip)

8:34 p.m. CDT Sunday: More than 250,000 customers have been impacted by power outages in Louisiana and Texas as of Sunday night.

Power outages from Harvey

7:50 p.m. CDT Sunday: Several ports along the Texas coast will remain closed on Monday including the Port of Houston and the Port of Galveston.

"All Port Houston facilities will be closed tomorrow, Monday, Aug. 28, due to the continued threat of inclement weather," officials wrote on the port's Facebook page. "We will be continuing to monitor the developing weather conditions to determine whether operations can safely resume on Tuesday. Updates will be provided as more information is available."

Houston's Johnson Space Center will also be closed Monday with the exception of essential personnel.

The Mission Control Center remains operational and fully capable of supporting the International Space Station from Houston," NASA said on its website.

7:19 p.m. CDT Sunday: The Federal Emergency Management Agency (FEMA) has more than 400 Urban Search and Rescue personnel working in south Texas with another 500-plus personnel situated elsewhere in the state.

In addition, the Coast Guard has 420 personnel conducting rescue missions and has deployed 16 helicopters with eight more inbound. The Coast Guard confirmed more than 2,000 rescues of multi-person cases through 3 p.m. Sunday.

“This remains a significant, deadly storm, and must not be underestimated,” said FEMA Administrator Brock Long. “With the continuing widespread flooding and devastation, every person in its path should heed the warnings of their local officials.”

6:29 p.m. CDT Sunday: Floating fire ants are adding to the dangers posed by floodwaters in Houston, Texas. The ants band together to create rafts to survive the high waters, floating until they reach a dry area. A fire ant's bite can cause painful, stinging blisters.