Floodwaters grounded flights at Houston’s largest airport and shut down major roads throughout southeastern Texas Thursday — the heaviest rainfall since Hurricane Harvey slammed the city in 2017.

The remnants of Tropical Rainstorm Imelda, which made landfall about 65 miles southeast of the city Tuesday, has dropped 40 inches of rain in the greater Houston area — including more than 25 inches over a 12-hour period.

That could end up at 55 inches in some suburbs and up to a foot in the central city before the storms dissipate, AccuWeather reported.

“Houston could be looking at 6 to 12 inches of rain,” said Dan Kottlowski, a senior meteorologist and lead hurricane expert for AccuWeather. “This is about a third of that amount (from Harvey) right now, but this is the worst flooding they’ve seen since Harvey.”

Harvey hit the region with 130 mph winds, killing as many as 80 and causing more than $125 billion in damages — dropping as much as 51 inches of rain in downtown Houston.

Jeff Evans, the meteorologist in charge at the National Weather Service in Houston, said the suburbs could see more accumulation than when Harvey came through. But the center city, buried in three feet of water by Harvey, shouldn’t see those levels nor the same deadly winds.

But it doesn’t take much, he said.

“It’s hard to compare storms,” Evans said. “Some totals are a little bigger, but Houston is such a gigantic blueprint…. Typically for Houston, when you get to 2 or 3 inches, you really start overwhelming the capacity of the storm drain system.”

He said the flooding from Imelda hit hardest east and southeast of the city, but flooding has caused problems — George Bush Intercontinental Airport was forced to ground departing flights on Thursday.

In Jefferson County, the sheriff’s office reported on Facebook that the Green Pond Gulley Levy, which holds up to 5,600 acres of water, was “deteriorating and could break at any moment.”

The Beaumont Police Department urged residents to seek high ground as rising floodwaters began to inundate homes and shut down major roadways, including sections of Interstate 10 and Highway 69.

“The situation here is turning worse by the minute,” Michael Stephens, a resident of nearby Vidor, told CNN. “People have snakes in their apartments from the creek.”