More than 40 million Americans under heat alerts as high temperatures hit South

More than 40 million Americans are under heat alerts as scorching high temperatures continue for Texas, Louisiana, Mississippi and Florida. Meanwhile, a multi-day severe weather outbreak is stretching from the plains into the south.

Excessive Heat warnings are in effect for major cities like Houston, San Antonio and New Orleans.

The combination of heat and oppressive humidity will lead to heat index values of 110 degrees to 120 degrees on Saturday afternoon.

Overnight, low temperatures have been setting records for how warm they are. Houston didn’t drop below 82 degrees on Friday and San Antonio tied a "warmest low temperature" record for the month of June at 80 degrees.

This cumulative heat offers no relief, and often contributes to potentially deadly heat exhaustion.

Since Tuesday, there have been well over 1,000 severe storm reports, ranging from damaging wind and flooding in Pensacola, Florida, to the deadly EF-2 tornado in Perryton, Texas. There was even a confirmed EF-0 tornado in New Jersey on Friday, but that severe weather threat in the Mid-Atlantic and Northeast has since ended.

Saturday's risk covers a huge area and includes more than 36 million Americans from Colorado to Florida. Damaging winds and large hail are the main threats for most of this area, but there is a risk for powerful tornadoes around Oklahoma.

On Sunday, there is yet another chance for significant storms. An Enhanced Risk is already in the outlook from Arkansas to Alabama. All modes of severe weather are possible in this area.