CNN
 — 

More than 700,000 people across the Southeast and Ohio Valley are in the dark Sunday night as powerful storms ripped through the US, unleashing strong winds, hail and tornado threats.

Thunderstorms battered parts of Arkansas, Tennessee, Mississippi and parts of the Ohio Valley Sunday evening and will continue to threaten the area through much of the night, the Storm Prediction Center said.

In the town of Bargersville, about 18 miles south of Indianapolis, authorities described a trail of destruction left in the aftermath of a possible tornado.

There were “at least 75 homes with moderate to severe damage” from the possible twister, Bargersville Community Fire Department Chief Eric Funkhouser said, adding the storm also “took down” an apartment complex that was under construction.

There were no serious injuries, the chief said, but the storm left behind “roughly three miles” of damage.

National Weather Service Meteorologist Joseph Nield told CNN that footage they’ve viewed of the possible twister led them to be “virtually certain” the storm was a tornado. But, Nield added, a survey team will make a final determination Monday.

Videos posted on social media showed a twister-shaped cloud ripping through buildings and tossing around debris. Footage of the aftermath showed several houses with their roofs ripped off and uprooted trees scattered in nearby debris.

Officials in Bargersville told residents in one area to prepare to be without power for the next 48 hours.

Storms moving along the Ohio River across northern Kentucky and southern Indiana Sunday evening also led to reports of large hail, the Storm Prediction Center said.

More than 6 million people were under an enhanced risk for severe weather Sunday night, including in Nashville, Tennessee; Louisville, Kentucky; and Pine Bluff, Arkansas. More than 18 million were under a slight risk level in areas including Memphis; Cincinnati; Birmingham and Columbus, Georgia, according to the prediction center.

The storms came as more than 50 million people from Arizona to Louisiana faced “oppressive” heat Sunday, in a significant heat wave that is forecast to spread and continue through the beginning of the July 4th holiday week and potentially break several high temperature records across the region.

The heat alerts include much of Texas as well as parts of Arizona, New Mexico, Oklahoma, Arkansas, Louisiana, Mississippi and Tennessee, according to the National Weather Service.

“The oppressive heat wave in the south-central U.S. shows no signs of letting up,” the Weather Prediction Center said Sunday afternoon. “Widespread heat-related advisories are in effect for southern Arizona and New Mexico and across most of Texas as temperatures soar once again into the 100s.”

Dangerously high temperatures are forecast to expand into the central Plains and Middle and Lower Mississippi Valley by the middle of the week.

The persistent heat will become “increasingly dangerous and potentially deadly” to those in south and south-central Texas, the weather service has warned, as “many locations in those parts of Texas have already experienced a yearly record number of hours of dangerously high heat index readings.”

The extreme heat is particularly impacting Texas and contributed to at two deaths Friday at the remote Big Bend National Park.

A father and his two stepsons were hiking the Marufo Vega Trail in extreme heat Friday – with temperatures of 119 degrees – when the 14-year-old stepson fell ill and lost consciousness, the National Park Service said in a news release.

The father, 31, hiked to their vehicle to find help, while the other stepson, 21, tried to carry his brother to the trailhead, the service said.

Emergency responders later reached the 14-year-old dead along the trial, the service said. The father’s vehicle was found crashed over an embankment, and he was pronounced dead at the scene, the service said. No further details were provided about the 21-year-old.

The heat has also raised concerns about the capacity of the state’s power authority, the Electric Reliability Council of Texas, known as ERCOT.

ERCOT said a “Weather Watch” will run through June 30, according to a Facebook post.

In Austin, the state capital, multiple Parks and Recreation centers serving as cooling centers are extending their normal operating hours to 8 p.m. CT, the city’s website said. All public libraries, except for three, are also extending their hours until 8 p.m., the city added.

The Travis County Community Centers are also serving as cooling centers on Sunday during normal business hours, the city said. Those without transportation to one of the cooling centers can catch a free ride on a city bus, Austin’s Emergency Medical Service public information officer told CNN in an email Sunday.

The city’s Community Health Paramedic program, “has been visiting and checking in with … unhoused neighbors, especially those who are particularly isolated,” and “handing out cases of water for people and pets alike,” the spokesperson told CNN.

Houston opened two “multi-service centers” and a community center as cooling locations Sunday for residents without adequate air conditioning.

The YMCA and dozens of Houston public libraries can also be used as cooling centers, the Houston Health Department said in a release.

“People may seek air-conditioning in city multi-service centers, libraries and recreation centers during normal business hours, even when the Public Health Heat Emergency Plan is not activated,” the department said.

The city will provide free transportation to and from the various cooling centers.

A statement posted on social media by Harris County Judge Lina Hidalgo announced an American Red Cross emergency shelter opened Saturday afternoon near Houston to help those who are still without power from storms earlier in the week.

Further, Corpus Christi made six public libraries available to residents as cooling centers over the weekend, the city announced in a Friday news release. The city said residents would be able to obtain free public transport to the cooling centers.