Residents of coastal southeast Texas were urged to seek higher ground Wednesday morning as forecasters warned of dangerous flash flooding.

Heavy rain was falling in Victoria, Corpus Christi and McAllen, where hundreds of migrants seeking entry into the United States await processing at a detention center. There were no immediate reports of problems at the center because of the rain.

Flash flood warnings were issued for southeast Hidalgo and northwest Cameron counties, along the Mexican border. Also expected to experience flooding are Port Aransas, Ingleside, Edinburg, Mission, Pharr, San Juan, Alamo, Donna, Hidalgo, Elsa, Palmhurst and North McAllen, the weather service said.

CNN images from McAllen showed stranded vehicles with water almost covering the tires.

“This is a PARTICULARLY DANGEROUS SITUATION. SEEK HIGHER GROUND NOW!” the weather service said.

Flash flooding was reported in Hidalgo County, already saturated with 4 to 6 inches of rain. Meteorologists predict another 2 to 4 inches of rain Wednesday across southeastern coastal Texas.

The Corpus Christi office of the weather service tweeted that 12.89 inches of rain had fallen between 7 a.m. Monday and 7 a.m. Wednesday in the city’s northwest section.

Flash flood watches are also in effect for areas south of Houston to Brownsville, at the Mexican border, with flash flood warnings popping up as storms flare, CNN meteorologists said.

Showers and thunderstorms are forecast to continue through Thursday, the National Weather Service tweeted.

The system producing the rainfall is not a tropical system, CNN meteorologist Brandon Miller said, but it does contain ample amounts of tropical moisture and is dumping it at rates normally found in a tropical storm.

‘Nervous about losing their stuff again’

Rain also continued to fall near Houston, causing more misery for places still reeling from the impact of Hurricane Harvey last summer. Flash flood watches were issued Wednesday for areas southwest of Houston and could be “extended eastward during the day,” the weather service’s local office said.

North of Houston, the city of Port Arthur, which along with Beaumont was devastated in August by Harvey’s floods, was swamped again Tuesday by the weather system now pummeling points south.

Video from Port Arthur showed streets turned into raging rivers as cars slowly made their way through them.

The storms conjured memories of last summer’s flooding, said Damion Robertson, of Port Arthur.

“It’s concerning. A lot of people just lost a lot of houses … over Harvey,” Robertson told CNN affiliate KBTV. “So, a lot of people are probably nervous about losing their stuff again.”

Larry Wolf, of Port Arthur, said his home has flooded twice.

“I’m to the point where I’m 75 years old,” he told KBTV. “I can’t do it anymore.”

The Beaumont Port Arthur airport “broke daily rainfall record (Tuesday), where 5.89 inches of rain fell in a 24-hour period, causing flash flooding in the area,” CNN meteorologist Michael Guy said Wednesday.

“While rainfall totals will not even come close to the amount that Harvey left in its wake, the region could still suffer damage from flash flooding, downed trees and travel disruptions,” he said.

Harvey dumped record rainfall of more than 60 inches over just a few days after it hit southeast Texas as a Category 4 storm. Dozens of people died and millions were affected in and around Houston, the nation’s fourth-largest city, and along the Gulf Coast.