An unprecedented and perilous US heat wave, responsible for the tragic deaths of at least 14 individuals in Texas and Louisiana, persists on Thursday, enveloping a significant portion of the southern United States, according to USA Today.

The region is grappling with scorching temperatures exceeding 100 degrees Fahrenheit and punishing humidity levels.

The life-threatening heat will afflict a vast stretch of the nation, spanning from southeast New Mexico through the Southern Plains, eastern Kansas, the Lower Mississippi Valley, the Lower Ohio Valley, the Lower Tennessee Valley, and the central Gulf coastal region, according to the National Weather Service.

Authorities have issued warnings to alert residents of the potential dangers.

Thursday is expected to bring the most intense heat of the season thus far for many areas outside of Texas. Over 80 million Americans reside in areas where heat alerts are in effect.

The cities of Dallas, Houston, New Orleans, Jackson, Little Rock, Memphis, and Nashville are anticipated to face the brunt of the extreme temperatures in the coming days.

Heat index values, which consider humidity and indicate how hot it feels to the human body, are projected to reach between 110 and 120 in these areas.

The weather service tweeted a reminder on Wednesday: "Heat is the leading cause of weather-related deaths each year. Take it seriously."

This deadly heat wave sets new records and serves as a grave reminder of the hazards associated with extreme temperatures.

Authorities and health officials urge individuals to exercise caution and take necessary precautions to protect themselves during this dangerous weather event.

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US Heat Wave Forecast

As the Fourth of July approaches, the heat index across the United States is soaring, reaching dangerous levels in southern states just before the holiday celebrations.

Over 100 million people were under excessive heat advisories nationwide on Thursday. The USA TODAY Heat Index reported heat indexes over 115 degrees in certain parts of the US, considering the combined effects of heat and humidity.

Here is a summary of the weather conditions expected across the country for the upcoming weekend:

Friday's forecast indicates that the heat index will remain steady across most parts of the country. In the southern states, including Texas, Mississippi, Louisiana, Alabama, and Arkansas, more areas will likely experience heat indexes exceeding 115 degrees.

The heat index is expected to rise in certain regions on Saturday. The northern parts of the US can anticipate highs around 90 degrees.

Although the Gulf Coast will experience slightly less intense heat, southern Texas may see an increase, with the heat index forecasted to reach 115 degrees in some areas.

Heat indexes are predicted to cool slightly in some southern states, with Mississippi, Alabama, and Louisiana expecting indexes between 105 and 110 degrees Sunday.

However, parts of southern Texas and Florida could experience rising heat indexes, with some areas forecasted to surpass 115 degrees.

Washington, Idaho, Colorado, and Wyoming will likely have heat indexes in the 70s and 80s, while Pennsylvania, New York, Massachusetts, Vermont, and Maine can expect similar ranges.

Most of the Midwest is expected to see heat indexes ranging from 80 to 95 degrees.

What Causes US Heat Wave?

Studies have consistently highlighted the link between climate change and extreme heat events' increased frequency, severity, and duration.

Recent research conducted by Climate Central, a nonprofit research group based in New Jersey, revealed that human-caused global warming had made the ongoing heatwave in Texas and Mexico at least five times more likely to occur, per NBC News.

Simultaneously, climate change's effects also contribute to poor air quality in certain regions. Smoke from wildfires in Canada has led to concerns about air pollution, impacting approximately 87 million individuals in the Midwest and parts of the Northeast.

The heat dome responsible for the scorching conditions is anticipated to expand northward into the Middle Mississippi Valley, according to the National Weather Service's early Wednesday update.

As a result, high temperatures will persist, offering minimal respite during the overnight hours.

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Written by: Bert Hoover

WATCH: Dangerous heat wave plagues southern U.S. with 45 million people under heat advisories - From PBS NewsHour