Extreme heat is forecast to threaten Texas residents again this week, with advisories in place through Thursday night. 

The National Weather Service (NWS) office in Fort Worth said high temperatures were forecast in the triple digits. 

The agency's office for Austin and San Antonio said the city of San Antonio – in southwest Texas – tied a record high temperature on Wednesday for that date.

Widespread dangerous heat indexes will stretch from the Lone Star State to the Northeast and across Montana. 

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All Texas mainstem rivers are below 10% of their normal flow, according to the NWS West Gulf River Forecast Center and three active large wildfires continue to burn there.

The heat wave is putting nearly 80 million Americans at risk of heat-related illness, according to FOX Weather. 

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Power use in Texas is expected to break records again this week, according to its grid operator. 

The Electric Reliability Council of Texas (ERCOT) said it has enough resources to meet such demand. 

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ERCOT has previously faced criticism after a February 2021 winter storm became deadly, with millions of Texans left without water, power and heat.

The U.S. is expected to use record amounts of power this year

Reuters contributed to this report.