Around 55 million Americans are under heat alerts as the heat index hits triple digits across the South.

Record highs were broken across major cities in Texas and Louisiana on Monday, with more high temperatures impacting those areas on Tuesday.

The heat index -- or "feels like" temperature -- in Shreveport, Louisiana, reached 111 degrees Tuesday, while New Orleans was at 109 degrees.

In Texas, Dallas and Austin reached a heat index of 108 and 106 degrees, respectively, on Tuesday, while Corpus Christi had a scorching 112-degree heat index.

The heat index in Oklahoma City was 106 degrees, while Joplin, Missouri, was at 110.

The relentless and oppressive heat will be the main story through the week for places like Austin, Dallas, New Orleans, Shreveport, Jackson, Little Rock and Wichita; all are under excessive heat warnings for temperatures near 100 degrees, with the heat index well above 100.

It will feel like 100 to over 110 degrees for Dallas, Austin, Little Rock and New Orleans through at least Friday and possibly beyond, according to meteorologists.

Arizona is finally catching a break this week as monsoonal storms and clouds move in, but unfortunately, that break isn't anticipated to last long, according to experts.

Phoenix and Tucson are already under another excessive heat watch as the temperatures soar back up and over 110 by the end of the work week and into the weekend.

Residents in Arizona's capital have experienced weeks of temperatures at or above 110 degrees Fahrenheit.

July was Phoenix’s hottest month on record, experts said.

Last week, the medical examiner's office in Arizona's Maricopa County was over capacity and had to bring in refrigeration units because of a spike in deaths in July amid a record-breaking heat wave, officials said.

In other parts of the country, flood watches are in effect for several states across the Rockies and Plains -- including New Mexico, Colorado, Wyoming, Nebraska, Kansas and Missouri.

Another day of monsoon storms could impact parts of the southern Rockies on Tuesday, with heavy rain and severe storms being possible in northeast Colorado.

Heavy rain could bring flooding to central Missouri late Tuesday night into early Wednesday.