Texas Gov. Greg Abbott has declared a disaster in 13 counties as Tropical Storm Imelda brought torrential rain and dangerous flash flooding to the Houston area, stranding residents in their homes, drivers in their cars and canceling hundreds of flights at local airports.
Over 900 flights were canceled into and out of Houston area airports due to the severe rain, which reached over 40 inches in some spots.
The storm claimed its first lives on Thursday as well. A man in Jefferson County was "electrocuted and drowned" while trying to move his horse, according to the sheriff's office. The family of Hunter Morrison, the man killed, said he was not trying to rescue any people, as had been reported locally, and wanted to correct false reports.
A second death was reported in Harris County, which includes Houston, as a man drowned after driving his van into floodwaters and became submerged, according to the sheriff's office.
Houston broke its record for the most rain in one day in the month of September with over 9 inches.
The town of Hamshire, Texas, saw six months' worth of rain in 48 hours. More than 33 inches of rain has fallen in Hamshire since Tuesday -- and over 2 feet of that rainfall within 12 hours. A preliminary total of 43.15 inches from the storm was measured in Jefferson County, according to the National Weather Service.
In the small town of Winnie, Texas, the conditions are "horrible," with rapidly-rising floodwaters making roads impassable, Chambers County Sheriff Brian Hawthorne told ABC News as the rain pounded down Thursday.
"This is the worst flooding I’ve ever seen," Hawthorne said.
Houses flooded during Hurricane Harvey two years ago are now taking in water again; some homes have 4 to 5 feet of water inside, said Hawthorne.
Anna Avales' home in Winnie is still recovering from flooding during Harvey. She called Thursday's rain "devastating" and is "hoping and praying that it stops."
James Gibson and his wife walked ABC News through their Chambers County home, where the wood floors are now submerged under roughly 8 inches of water.
The rain fell “too fast to do anything” he said.
"Until it quits raining, it's gonna be a nightmare," the sheriff said.
Over 300 people were rescued from homes in Chambers County as the water rose, local officials said.
Dump trucks and airboats were being used to get residents to safety.
The threat isn't over.
The relentless, heavy rain is continuing to slam parts of southeastern Texas and southwestern Louisiana Thursday afternoon. It'll taper off Thursday evening leaving lingering, scattered showers.
But thunderstorms and downpours are possible again on Friday.
Up to 4 inches of rain could still fall in the hard-hit areas from Houston to Beaumont from Thursday afternoon to Friday afternoon.
The remains of Tropical Storm Imelda with then track inland and bring areas of heavy rain -- up to 4 inches -- to east Texas and northwestern Louisiana.
ABC News' Clayton Sandell and Will Gretsky contributed to this report.