(CNN) — Nine people have died in the last eight days due to heat-related illnesses in Webb County, Texas, the county medical examiner said.

“I come to you with a heavy heart this morning. In the last eight days in our county, we’ve lost nine residents to this heat,” Webb County Medical Examiner Dr. Corinne Stern said at a commissioners court meeting Tuesday.

Power use in Texas hit an all-time high Tuesday, the state’s power authority said, and the blistering temperatures that prompted the usage surge will continue to scorch parts of the US Wednesday – putting nearly 90 million people under heat alerts.

As customers grappled with triple-digit heat, the Texas Electric Reliability Council said power usage reached 80,828 megawatts at 6 p.m. Tuesday. That surpassed the grid’s previous record of 80,148 megawatts, set on July 20, 2022. The authority expects another record to be set Wednesday afternoon.

The state’s power grid is largely cut off from the rest of the country and has seen frequent challenges in recent years as Texans have been faced with extreme heat and other strains, including severe storms and tornadoes.

While the Texas power authority has assured residents the energy supply is sufficient to avoid blackouts, it is asking residents to cut back on power usage where possible.

The heat wave that has impacted Texas for well over a week is set to expand northward and eastward. More than 150 heat records could be broken during the next six days. The National Weather Service in Memphis warned the warm front could bring dangerous peaks of 110 to 115 degrees Thursday and Friday.

Several daily high-temperature records were broken or tied Tuesday in Texas, including at Houston Hobby Airport, Corpus Christi, Laredo and Del Rio. Del Rio hit 110 degrees, marking its 10th consecutive day of record highs.

On Wednesday, 100-degree heat will spread northward into Oklahoma and Kansas, as well as eastward into Arkansas and Louisiana. Oklahoma City is expecting a record high of 106, the weather service said.

The heat index – what the body feels – will range from 100 to 115 degrees across large portions of the central and southern Plains as well as into the lower Mississippi Valley. Temperatures will continue to reach 100 degrees across much of Texas, Louisiana, Oklahoma, Kansas and Arkansas on Thursday and will also spread into portions of Missouri, Illinois, Tennessee, Mississippi and Alabama.

Heat alerts are also posted for portions of Colorado and California. The heat in southeastern Colorado should peak Wednesday, with highs from the upper 90s to around 100 degrees.

In California, the heat will peak on Friday and Saturday, with highs climbing to 110. That includes much of the Sacramento and San Joaquin valleys, as well as a large portion of the Central Coast and Bay Area. Mount Shasta could come close to breaking its 100-degree record high on Friday, with a high of 99 degrees forecast.

More than 600 people in the United States are killed by extreme heat every year, according to the US Centers for Disease Control and Prevention.

As Americans face hotter and hotter temperatures, officials are urging people to take safety precautions, including staying hydrated, avoiding leaving pets and kids in cars unattended and finding cool, indoor spaces to wait out the heat.

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