By Meteorologists Chris Dolce, Mary Gilbert, and CNN’s Hanna Park

(CNN) — Another round of slow-moving storms packing heavy rain is pounding an already drenched area of southern Texas Wednesday, again raising the potential of life-threatening flooding.

The relentless rain, up to 16 inches of it so far, has led to dozens of water rescues in the region and forecasters are warning of more rainfall that could be catastrophic. More than half a year’s worth of rain could fall in the hardest-hit areas by the end of the week, according to the National Weather Service.

Wednesday marks the second consecutive day the Weather Prediction Center has issued its highest risk of flooding rain. It’s the first time the agency has issued the alert on back-to-back days since April 2025.

The area facing additional downpours includes Texas Hill Country, which saw devastating flash flooding last July that left more than 130 dead, including 25 girls and two counselors at Camp Mystic.

Flash flood warnings were issued once again for hard-hit Uvalde County and other nearby counties on Wednesday morning. At least 45 people had been pulled from floodwater in the county by the end of Tuesday. Multiple additional rescues were carried out in neighboring Medina County and Texas Gov. Greg Abbott issued a disaster declaration for 59 counties on Tuesday.

The storms also spawned a tornado near Interstate 10 northwest of San Antonio around 8 a.m. CT on Wednesday. CNN has reached out to Bexar County officials to see if the twister caused any damage, but video posted to social media showed power flashes and debris swirling in the air.

‘Worst-case scenario’ for flooding

The escalated flood threat Wednesday includes rounds of heavy, slow-moving rainfall on top of areas already soaked by 6 to 16 inches of it since Monday night. The threat of catastrophic flooding won’t ease up until Friday, as storms drop rain at 2 to 4 inches per hour.

• Through Wednesday night: The areas most at risk of dangerous flash flooding are nearly identical to the ones that were deluged on Tuesday, including parts of the western Hill Country, the Edwards Plateau and the Rio Grande Valley near the US-Mexico border. A Level 4 of 4 high risk of flooding rainfall is in place here, with an additional 10 to 20 inches of rain possible through the end of the week.

This type of pattern where storms repeatedly hit the same areas is a “worst-case scenario,” according to the Weather Prediction Center.

The ground is already soaked so it will take less rain to trigger serious flooding with any rain more quickly turning to runoff instead of soaking into the ground. Considerable to locally catastrophic impacts are possible along portions of the US 90 corridor west of San Antonio, the WPC said.

Areas surrounding the high risk zone are under a very serious Level 3 of 4 flooding rainfall risk, and a Level 2 of 4 risk extends as far east as Houston.

Flooding is likely on roads and in urban areas, and some homes could be inundated, the WPC warned. Creeks, streams and rivers will rise, with some going above flood stage.

• Thursday: The area at greatest risk of flash flooding in Texas will shrink some but will still include some of the hardest-hit areas. Anywhere from Del Rio to Midland and San Angelo could see additional flooding.

• Friday: Drenching storms will start to ease considerably on Friday, with a lower-level flood threat lingering mainly in the western part of the state.

Why this keeps happening

Extreme rainfall events like this are becoming more common as planet-warming pollution drives temperatures higher, because warmer air holds more moisture – which storms can then wring out like a water-laden sponge in heavy, localized downpours.

The Hill Country is especially prone to flooding issues because its steep slopes, shallow soils and exposed bedrock repel heavy rain instead of absorbing it.

Fueling the threat is abundant Gulf moisture clashing with a stalled front and a pocket of energy in the upper atmosphere – a notorious recipe for slow-moving clusters of storms that can unleash 2 to 4 inches of rain an hour.